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The European Space Agency (ESA; French: Agence spatiale europenne, ASE;[4][5] German: Europische Weltraumorganisation) is an intergovernmental organisation of 22 member states[6] dedicated to the exploration of space. Established in 1975 and headquartered in Paris, France, ESA has a worldwide staff of about 2,000[7] and an annual budget of about 5.25 billion / US$5.77 billion (2016).[8]

ESA’s space flight programme includes human spaceflight (mainly through participation in the International Space Station programme); the launch and operation of unmanned exploration missions to other planets and the Moon; Earth observation, science and telecommunication; designing launch vehicles; and maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana. The main European launch vehicle Ariane 5 is operated through Arianespace with ESA sharing in the costs of launching and further developing this launch vehicle.

The agency’s facilities are distributed among the following centres:

After World War II, many European scientists left Western Europe in order to work with the United States. Although the 1950s boom made it possible for Western European countries to invest in research and specifically in space-related activities, Western European scientists realised solely national projects would not be able to compete with the two main superpowers. In 1958, only months after the Sputnik shock, Edoardo Amaldi (Italy) and Pierre Auger (France), two prominent members of the Western European scientific community, met to discuss the foundation of a common Western European space agency. The meeting was attended by scientific representatives from eight countries, including Harrie Massey (United Kingdom).

The Western European nations decided to have two agencies: one concerned with developing a launch system, ELDO (European Launch Development Organization), and the other the precursor of the European Space Agency, ESRO (European Space Research Organisation). The latter was established on 20 March 1964 by an agreement signed on 14 June 1962. From 1968 to 1972, ESRO launched seven research satellites.

ESA in its current form was founded with the ESA Convention in 1975, when ESRO was merged with ELDO. ESA had ten founding member states: Belgium, Denmark, France, Germany, Italy, the Netherlands, Spain, Sweden, Switzerland and the United Kingdom.[9] These signed the ESA Convention in 1975 and deposited the instruments of ratification by 1980, when the convention came into force. During this interval the agency functioned in a de facto fashion. ESA launched its first major scientific mission in 1975, Cos-B, a space probe monitoring gamma-ray emissions in the universe, which was first worked on by ESRO.

The ESA collaborated with NASA on the International Ultraviolet Explorer (IUE), the world’s first high-orbit telescope, which was launched in 1978 and operated successfully for 18 years. A number of successful Earth-orbit projects followed, and in 1986 ESA began Giotto, its first deep-space mission, to study the comets Halley and GriggSkjellerup. Hipparcos, a star-mapping mission, was launched in 1989 and in the 1990s SOHO, Ulysses and the Hubble Space Telescope were all jointly carried out with NASA. Later scientific missions in co-operation with NASA include the CassiniHuygens space probe, to which ESA contributed by building the Titan landing module Huygens.

As the successor of ELDO, ESA has also constructed rockets for scientific and commercial payloads. Ariane 1, launched in 1979, carried mostly commercial payloads into orbit from 1984 onward. The next two versions of the Ariane rocket were intermediate stages in the development of a more advanced launch system, the Ariane 4, which operated between 1988 and 2003 and established ESA as the world leader[citation needed] in commercial space launches in the 1990s. Although the succeeding Ariane 5 experienced a failure on its first flight, it has since firmly established itself within the heavily competitive commercial space launch market with 82 successful launches until 2018. The successor launch vehicle of Ariane 5, the Ariane 6, is under development and is envisioned to enter service in the 2020s.

The beginning of the new millennium saw ESA become, along with agencies like NASA, JAXA, ISRO, CSA and Roscosmos, one of the major participants in scientific space research. Although ESA had relied on co-operation with NASA in previous decades, especially the 1990s, changed circumstances (such as tough legal restrictions on information sharing by the United States military) led to decisions to rely more on itself and on co-operation with Russia. A 2011 press issue thus stated:[10]

Russia is ESA’s first partner in its efforts to ensure long-term access to space. There is a framework agreement between ESA and the government of the Russian Federation on cooperation and partnership in the exploration and use of outer space for peaceful purposes, and cooperation is already under way in two different areas of launcher activity that will bring benefits to both partners.

Notable outcomes are ESA’s include SMART-1, a probe testing cutting-edge new space propulsion technology, the Mars Express and Venus Express missions, as well as the development of the Ariane 5 rocket and its role in the ISS partnership. ESA maintains its scientific and research projects mainly for astronomy-space missions such as Corot, launched on 27 December 2006, a milestone in the search for exoplanets.

The treaty establishing the European Space Agency reads:[11]

ESA’s purpose shall be to provide for, and to promote, for exclusively peaceful purposes, cooperation among European States in space research and technology and their space applications, with a view to their being used for scientific purposes and for operational space applications systems

ESA is responsible for setting a unified space and related industrial policy, recommending space objectives to the member states, and integrating national programs like satellite development, into the European program as much as possible.[11]

Jean-Jacques Dordain ESA’s Director General (2003-2015) outlined the European Space Agency’s mission in a 2003 interview:[12]

Today space activities are pursued for the benefit of citizens, and citizens are asking for a better quality of life on Earth. They want greater security and economic wealth, but they also want to pursue their dreams, to increase their knowledge, and they want younger people to be attracted to the pursuit of science and technology.

I think that space can do all of this: it can produce a higher quality of life, better security, more economic wealth, and also fulfill our citizens’ dreams and thirst for knowledge, and attract the young generation. This is the reason space exploration is an integral part of overall space activities. It has always been so, and it will be even more important in the future.

ESA describes its work in two overlapping ways:

According to the ESA website the activities are:

Every member country must contribute to these programmes, listed according to:[13]

Depending on their individual choices the countries can contribute to the following programmes, listed according to:[14]

ESA member states

ESA associate members

Signatories of the Cooperation Agreement

By 2015, ESA was an intergovernmental organisation of 22 member states.[6] Member states participate to varying degrees in the mandatory (25% of total expenditures in 2008) and optional space programmes (75% of total expenditures in 2008).[15] The 2008 budget amounted to 3.0 billion the 2009 budget to 3.6 billion.[16] The total budget amounted to about 3.7 billion in 2010, 3.99 billion in 2011, 4.02 billion in 2012, 4.28 billion in 2013, 4.10 billion in 2014 and 4.33 billion in 2015.[17][18][19][20][21] Languages generally used are English and French. Additionally, official documents are also provided in German and documents regarding the Spacelab are also provided in Italian. If found appropriate, the agency may conduct its correspondence in any language of a member state.

The following table lists all the member states and adjunct members, their ESA convention ratification dates, and their contributions in 2016:[22]

Currently the only associated member state is Slovenia.[33] Previously associated members were Austria, Norway and Finland, all of which later joined ESA as full members.

Since 1 January 1979, Canada has had the special status of a Cooperating State within ESA. By virtue of this accord, the Canadian Space Agency takes part in ESA’s deliberative bodies and decision-making and also in ESA’s programmes and activities. Canadian firms can bid for and receive contracts to work on programmes. The accord has a provision ensuring a fair industrial return to Canada.[35] The most recent Cooperation Agreement was signed on 2010-12-15 with a term extending to 2020.[36][37] For 2014, Canada’s annual assessed contribution to the ESA general budget was 6,059,449.00 (CAD$8,559,050).[38] For 2017, Canada has increased its annual contribution to 21,600,000 (CAD$30,000,000).[39]

ESA is funded from annual contributions by national governments as well as from an annual contribution by the European Union (EU).[40]

The budget of ESA was 5.250 billion in 2016.[8] Every 34 years, ESA member states agree on a budget plan for several years at an ESA member states conference. This plan can be amended in future years, however provides the major guideline for ESA for several years.[citation needed] The 2016 budget allocations for major areas of ESA activity are shown in the chart on the right.[8]

Countries typically have their own space programmes that differ in how they operate organisationally and financially with ESA. For example, the French space agency CNES has a total budget of 2015 million, of which 755 million is paid as direct financial contribution to ESA.[41] Several space-related projects are joint projects between national space agencies and ESA (e.g. COROT). Also, ESA is not the only European governmental space organisation (for example European Union Satellite Centre).

After the decision of the ESA Council of 21/22 March 2001, the procedure for accession of the European states was detailed as described the document titled “The Plan for European Co-operating States (PECS)”.[42] Nations that want to become a full member of ESA do so in 3 stages. First a Cooperation Agreement is signed between the country and ESA. In this stage, the country has very limited financial responsibilities. If a country wants to co-operate more fully with ESA, it signs a European Cooperating State (ECS) Agreement. The ECS Agreement makes companies based in the country eligible for participation in ESA procurements. The country can also participate in all ESA programmes, except for the Basic Technology Research Programme. While the financial contribution of the country concerned increases, it is still much lower than that of a full member state. The agreement is normally followed by a Plan For European Cooperating State (or PECS Charter). This is a 5-year programme of basic research and development activities aimed at improving the nation’s space industry capacity. At the end of the 5-year period, the country can either begin negotiations to become a full member state or an associated state or sign a new PECS Charter.[43] Many countries, most of which joined the EU in both 2004 and 2007, have started to co-operate with ESA on various levels:

During the Ministerial Meeting in December 2014, ESA ministers approved a resolution calling for discussions to begin with Israel, Australia and South Africa on future association agreements. The ministers noted that concrete cooperation is at an advanced stage with these nations and that prospects for mutual benefits are existing.[65]

A separate space exploration strategy resolution calls for further co-operation with the United States, Russia and China on “LEO exploration, including a continuation of ISS cooperation and the development of a robust plan for the coordinated use of space transportation vehicles and systems for exploration purposes, participation in robotic missions for the exploration of the Moon, the robotic exploration of Mars, leading to a broad Mars Sample Return mission in which Europe should be involved as a full partner, and human missions beyond LEO in the longer term.”[65]

This article needs to be updated. Please update this article to reflect recent events or newly available information. (June 2015)

The political perspective of the European Union (EU) was to make ESA an agency of the EU by 2014,[66] although this date was not met. The EU is already the largest single donor to ESA’s budget and non-ESA EU states are observers at ESA.

ESA has a fleet of different launch vehicles in service with which it competes in all sectors of the launch market. ESA’s fleet consists of three major rocket designs: Ariane 5, Soyuz-2 and Vega. Rocket launches are carried out by Arianespace, which has 23 shareholders representing the industry that manufactures the Ariane 5 as well as CNES, at ESA’s Guiana Space Centre. Because many communication satellites have equatorial orbits, launches from French Guiana are able to take larger payloads into space than from spaceports at higher latitudes. In addition, equatorial launches give spacecraft an extra ‘push’ of nearly 500m/s due to the higher rotational velocity of the Earth at the equator compared to near the Earth’s poles where rotational velocity approaches zero.

The Ariane 5 rocket is ESA’s primary launcher. It has been in service since 1997 and replaced Ariane 4. Two different variants are currently in use. The heaviest and most used version, the Ariane 5 ECA, delivers two communications satellites of up to 10 tonnes into GTO. It failed during its first test flight in 2002, but has since made 82 consecutive successful flights until a partial failure in January 2018. The other version, Ariane 5 ES, was used to launch the Automated Transfer Vehicle (ATV) to the International Space Station (ISS) and will be used to launch four Galileo navigational satellites at a time.[67][68]

In November 2012, ESA agreed to build an upgraded variant called Ariane 5 ME (Mid-life Evolution) which would increase payload capacity to 11.5 tonnes to GTO and feature a restartable second stage to allow more complex missions. Ariane 5 ME was scheduled to fly in 2018[69], but the whole project was scrapped in favor of Ariane 6, planned to replace Ariane 5 in the 2020s.

ESA’s Ariane 1, 2, 3 and 4 launchers (the last of which was ESA’s long-time workhorse) have been retired.

Soyuz-2 (also called the Soyuz-ST or Soyuz-STK) is a Russian medium payload launcher (ca. 3 metric tons to GTO) which was brought into ESA service in October 2011.[70][71] ESA entered into a 340 million joint venture with the Russian Federal Space Agency over the use of the Soyuz launcher.[10] Under the agreement, the Russian agency manufactures Soyuz rocket parts for ESA, which are then shipped to French Guiana for assembly.

ESA benefits because it gains a medium payload launcher, complementing its fleet while saving on development costs. In addition, the Soyuz rocketwhich has been the Russian’s space launch workhorse for some 40 yearsis proven technology with a very good safety record. Russia benefits in that it gets access to the Kourou launch site. Due to its proximity to the equator, launching from Kourou rather than Baikonur nearly doubles Soyuz’s payload to GTO (3.0 tonnes vs. 1.7 tonnes).

Soyuz first launched from Kourou on 21 October 2011, and successfully placed two Galileo satellites into orbit 23,222 kilometres above Earth.[70]

Vega is ESA’s carrier for small satellites. Developed by seven ESA members led by Italy, it is capable of carrying a payload with a mass of between 300 and 1500kg to an altitude of 700km, for low polar orbit. Its maiden launch from Kourou was on 13 February 2012.[72]

The rocket has three solid propulsion stages and a liquid propulsion upper stage (the AVUM) for accurate orbital insertion and the ability to place multiple payloads into different orbits.[73][74]

Historically, the Ariane family rockets have been funded primarily “with money contributed by ESA governments seeking to participate in the program rather than through competitive industry bids. This [has meant that] governments commit multiyear funding to the development with the expectation of a roughly 90% return on investment in the form of industrial workshare.” ESA is proposing changes to this scheme by moving to competitive bids for the development of the Ariane 6.[75]

This section needs to be updated. Please update this article to reflect recent events or newly available information. (July 2011)

At the time ESA was formed, its main goals did not encompass human space flight; rather it considered itself to be primarily a scientific research organisation for unmanned space exploration in contrast to its American and Soviet counterparts. It is therefore not surprising that the first non-Soviet European in space was not an ESA astronaut on a European space craft; it was Czechoslovak Vladimr Remek who in 1978 became the first non-Soviet or American in space (the first man in space being Yuri Gagarin of the Soviet Union) on a Soviet Soyuz spacecraft, followed by the Pole Mirosaw Hermaszewski and East German Sigmund Jhn in the same year. This Soviet co-operation programme, known as Intercosmos, primarily involved the participation of Eastern bloc countries. In 1982, however, Jean-Loup Chrtien became the first non-Communist Bloc astronaut on a flight to the Soviet Salyut 7 space station.

Because Chrtien did not officially fly into space as an ESA astronaut, but rather as a member of the French CNES astronaut corps, the German Ulf Merbold is considered the first ESA astronaut to fly into space. He participated in the STS-9 Space Shuttle mission that included the first use of the European-built Spacelab in 1983. STS-9 marked the beginning of an extensive ESA/NASA joint partnership that included dozens of space flights of ESA astronauts in the following years. Some of these missions with Spacelab were fully funded and organizationally and scientifically controlled by ESA (such as two missions by Germany and one by Japan) with European astronauts as full crew members rather than guests on board. Beside paying for Spacelab flights and seats on the shuttles, ESA continued its human space flight co-operation with the Soviet Union and later Russia, including numerous visits to Mir.

During the latter half of the 1980s, European human space flights changed from being the exception to routine and therefore, in 1990, the European Astronaut Centre in Cologne, Germany was established. It selects and trains prospective astronauts and is responsible for the co-ordination with international partners, especially with regard to the International Space Station. As of 2006, the ESA astronaut corps officially included twelve members, including nationals from most large European countries except the United Kingdom.

In the summer of 2008, ESA started to recruit new astronauts so that final selection would be due in spring 2009. Almost 10,000 people registered as astronaut candidates before registration ended in June 2008. 8,413 fulfilled the initial application criteria. Of the applicants, 918 were chosen to take part in the first stage of psychological testing, which narrowed down the field to 192. After two-stage psychological tests and medical evaluation in early 2009, as well as formal interviews, six new members of the European Astronaut Corps were selected – five men and one woman.[76]

The astronauts of the European Space Agency are:

In the 1980s, France pressed for an independent European crew launch vehicle. Around 1978 it was decided to pursue a reusable spacecraft model and starting in November 1987 a project to create a mini-shuttle by the name of Hermes was introduced. The craft was comparable to early proposals for the Space Shuttle and consisted of a small reusable spaceship that would carry 3 to 5 astronauts and 3 to 4 metric tons of payload for scientific experiments. With a total maximum weight of 21 metric tons it would have been launched on the Ariane 5 rocket, which was being developed at that time. It was planned solely for use in low Earth orbit space flights. The planning and pre-development phase concluded in 1991; the production phase was never fully implemented because at that time the political landscape had changed significantly. With the fall of the Soviet Union ESA looked forward to co-operation with Russia to build a next-generation space vehicle. Thus the Hermes programme was cancelled in 1995 after about 3 billion dollars had been spent. The Columbus space station programme had a similar fate.

In the 21st century, ESA started new programmes in order to create its own crew vehicles, most notable among its various projects and proposals is Hopper, whose prototype by EADS, called Phoenix, has already been tested. While projects such as Hopper are neither concrete nor to be realised within the next decade, other possibilities for human spaceflight in co-operation with the Russian Space Agency have emerged. Following talks with the Russian Space Agency in 2004 and June 2005,[81] a co-operation between ESA and the Russian Space Agency was announced to jointly work on the Russian-designed Kliper, a reusable spacecraft that would be available for space travel beyond LEO (e.g. the moon or even Mars). It was speculated that Europe would finance part of it. A 50 million participation study for Kliper, which was expected to be approved in December 2005, was finally not approved by the ESA member states. The Russian state tender for the project was subsequently cancelled in 2006.

In June 2006, ESA member states granted 15 million to the Crew Space Transportation System (CSTS) study, a two-year study to design a spacecraft capable of going beyond Low-Earth orbit based on the current Soyuz design. This project was pursued with Roskosmos instead of the cancelled Kliper proposal. A decision on the actual implementation and construction of the CSTS spacecraft was contemplated for 2008. In mid-2009 EADS Astrium was awarded a 21 million study into designing a crew vehicle based on the European ATV which is believed to now be the basis of the Advanced Crew Transportation System design.[82]

In November 2012, ESA decided to join NASA’s Orion programme. The ATV would form the basis of a propulsion unit for NASA’s new manned spacecraft. ESA may also seek to work with NASA on Orion’s launch system as well in order to secure a seat on the spacecraft for its own astronauts.[83]

In September 2014, ESA signed an agreement with Sierra Nevada Corporation for co-operation in Dream Chaser project. Further studies on the Dream Chaser for European Utilization or DC4EU project were funded, including the feasibility of launching a Europeanized Dream Chaser onboard Ariane 5.[84][85]

ESA has signed co-operation agreements with the following states that currently neither plan to integrate as tightly with ESA institutions as Canada, nor envision future membership of ESA: Argentina,[86] Brazil,[87] China,[88] India[89] (for the Chandrayan mission), Russia[90] and Turkey.[91]

Additionally, ESA has joint projects with the European Union, NASA of the United States and is participating in the International Space Station together with the United States (NASA), Russia and Japan (JAXA).

ESA and EU member states

ESA-only members

EU-only members

ESA is not an agency or body of the European Union (EU), and has non-EU countries (Norway, and Switzerland) as members. There are however ties between the two, with various agreements in place and being worked on, to define the legal status of ESA with regard to the EU.[92]

There are common goals between ESA and the EU. ESA has an EU liaison office in Brussels. On certain projects, the EU and ESA co-operate, such as the upcoming Galileo satellite navigation system. Space policy has since December 2009 been an area for voting in the European Council. Under the European Space Policy of 2007, the EU, ESA and its Member States committed themselves to increasing co-ordination of their activities and programmes and to organising their respective roles relating to space.[93]

The Lisbon Treaty of 2009 reinforces the case for space in Europe and strengthens the role of ESA as an R&D space agency. Article 189 of the Treaty gives the EU a mandate to elaborate a European space policy and take related measures, and provides that the EU should establish appropriate relations with ESA.

Former Italian astronaut Umberto Guidoni, during his tenure as a Member of the European Parliament from 2004 to 2009, stressed the importance of the European Union as a driving force for space exploration, “since other players are coming up such as India and China it is becoming ever more important that Europeans can have an independent access to space. We have to invest more into space research and technology in order to have an industry capable of competing with other international players.”[94]

The first EU-ESA International Conference on Human Space Exploration took place in Prague on 22 and 23 October 2009.[95] A road map which would lead to a common vision and strategic planning in the area of space exploration was discussed. Ministers from all 29 EU and ESA members as well as members of parliament were in attendance.[96]

ESA has a long history of collaboration with NASA. Since ESA’s astronaut corps was formed, the Space Shuttle has been the primary launch vehicle used by ESA’s astronauts to get into space through partnership programmes with NASA. In the 1980s and 1990s, the Spacelab programme was an ESA-NASA joint research programme that had ESA develop and manufacture orbital labs for the Space Shuttle for several flights on which ESA participate with astronauts in experiments.

In robotic science mission and exploration missions, NASA has been ESA’s main partner. CassiniHuygens was a joint NASA-ESA mission, along with the Infrared Space Observatory, INTEGRAL, SOHO, and others. Also, the Hubble space telescope is a joint project of NASA and ESA. Future ESA-NASA joint projects include the James Webb Space Telescope and the proposed Laser Interferometer Space Antenna.[citation needed] NASA has committed to provide support to ESA’s proposed MarcoPolo-R mission to return an asteroid sample to Earth for further analysis.[citation needed] NASA and ESA will also likely join together for a Mars Sample Return Mission.[97]

Since China has started to invest more money into space activities, the Chinese Space Agency has sought international partnerships. ESA is, beside the Russian Space Agency, one of its most important partners. Recently the two space agencies cooperated in the development of the Double Star Mission.[98]

ESA entered into a major joint venture with Russia in the form of the CSTS, the preparation of French Guiana spaceport for launches of Soyuz-2 rockets and other projects. With India, ESA agreed to send instruments into space aboard the ISRO’s Chandrayaan-1 in 2008.[99] ESA is also co-operating with Japan, the most notable current project in collaboration with JAXA is the BepiColombo mission to Mercury.

Speaking to reporters at an air show near Moscow in August 2011, ESA head Jean-Jacques Dordain said ESA and Russia’s Roskosmos space agency would “carry out the first flight to Mars together.”[100]

With regard to the International Space Station (ISS) ESA is not represented by all of its member states:[101] 10 of the 21 ESA member states currently participate in the project: Belgium, Denmark, France, Germany, Italy, Netherlands, Norway, Spain, Sweden and Switzerland. Austria, Finland and Ireland chose not to participate, because of lack of interest or concerns about the expense of the project. The United Kingdom withdrew from the preliminary agreement because of concerns about the expense of the project. Portugal, Luxembourg, Greece, the Czech Republic, Romania and Poland joined ESA after the agreement had been signed. ESA is taking part in the construction and operation of the ISS with contributions such as Columbus, a science laboratory module that was brought into orbit by NASA’s STS-122 Space Shuttle mission and the Cupola observatory module that was completed in July 2005 by Alenia Spazio for ESA. The current estimates for the ISS are approaching 100 billion in total (development, construction and 10 years of maintaining the station) of which ESA has committed to paying 8 billion.[102] About 90% of the costs of ESA’s ISS share will be contributed by Germany (41%), France (28%) and Italy (20%). German ESA astronaut Thomas Reiter was the first long-term ISS crew member.

ESA has developed the Automated Transfer Vehicle for ISS resupply. Each ATV has a cargo capacity of 7,667 kilograms (16,903lb).[103] The first ATV, Jules Verne, was launched on 9 March 2008 and on 3 April 2008 successfully docked with the ISS. This manoeuvre, considered a major technical feat, involved using automated systems to allow the ATV to track the ISS, moving at 27,000km/h, and attach itself with an accuracy of 2cm.

As of 2013, the spacecraft establishing supply links to the ISS are the Russian Progress and Soyuz, European ATV, Japanese Kounotori (HTV), and the USA COTS program vehicles Dragon and Cygnus.

European Life and Physical Sciences research on board the International Space Station (ISS) is mainly based on the European Programme for Life and Physical Sciences in Space programme that was initiated in 2001.

According to Annex 1, Resolution No. 8 of the ESA Convention and Council Rules of Procedure,[4] English, French and German may be used in all meetings of the Agency, with interpretation provided into these three languages. All official documents are available in English and French with all documents concerning the ESA Council being available in German as well.

The EU flag is the one to be flown in space during missions (for example it was flown by ESA’s Andre Kuipers during Delta mission)

The Commission is increasingly working together towards common objectives. Some 20 per cent of the funds managed by ESA now originate from the supranational budget of the European Union.

However, in recent years the ties between ESA and the European institutions have been reinforced by the increasing role that space plays in supporting Europes social, political and economic policies.

The legal basis for the EU/ESA co-operation is provided by a Framework Agreement which entered into force in May 2004. According to this agreement, the European Commission and ESA co-ordinate their actions through the Joint Secretariat, a small team of ECs administrators and ESA executive. The Member States of the two organisations meet at ministerial level in the Space Council, which is a concomitant meeting of the EU and ESA Councils, prepared by Member States representatives in the High-level Space Policy Group (HSPG).

ESA maintains a liaison office in Brussels to facilitate relations with the European institutions.

In May 2007, the 29 European countries expressed their support for the European Space Policy in a resolution of the Space Council, unifying the approach of ESA with those of the European Union and their member states.

Prepared jointly by the European Commission and ESAs Director General, the European Space Policy sets out a basic vision and strategy for the space sector and addresses issues such as security and defence, access to space and exploration.

Through this resolution, the EU, ESA and their Member States all commit to increasing co-ordination of their activities and programmes and their respective roles relating to space.[106]

Space exploration is the discovery and exploration of celestial structures in outer space by means of evolving and growing space technology. While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic space probes and human spaceflight.

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.[1]

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States. The launch of the first human-made object to orbit Earth, the Soviet Union’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet Space Program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971. After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS[2] following STS-133 in March 2011, plans for space exploration by the U.S. remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020[3] was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.[4] The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low Earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as EarthMoon L1, the Moon, EarthSun L2, near-Earth asteroids, and Phobos or Mars orbit.[5]

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future crewed space missions. China, Russia, Japan, and India have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 20th and 21st century.

From the 1990s onwards, private interests began promoting space tourism and then public space exploration of the Moon (see Google Lunar X Prize).

The highest known projectiles prior to the rockets of the 1940s were the shells of the Paris Gun, a type of German long-range siege gun, which reached at least 40 kilometers altitude during World War One.[6] Steps towards putting a human-made object into space were taken by German scientists during World War II while testing the V-2 rocket, which became the first human-made object in space on 3 October 1942 with the launching of the A-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V-2 rocket on 10 May 1946.[7] The first images of Earth taken from space followed the same year[8][9] while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V-2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V-2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

The first successful orbital launch was of the Soviet uncrewed Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83kg (183lb), and is believed to have orbited Earth at a height of about 250km (160mi). It had two radio transmitters (20 and 40MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.

The first successful human spaceflight was Vostok 1 (“East 1”), carrying 27-year-old Russian cosmonaut Yuri Gagarin on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin’s flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard’s suborbital flight on Freedom 7. Orbital flight was achieved by the United States when John Glenn’s Friendship 7 orbited Earth on 20 February 1962.

Valentina Tereshkova, the first woman in space, orbited Earth 48 times aboard Vostok 6 on 16 June 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on 15 October 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Divine Vessel 5) spacecraft.

The first artificial object to reach another celestial body was Luna 2 in 1959.[10] The first automatic landing on another celestial body was performed by Luna 9[11] in 1966. Luna 10 became the first artificial satellite of the Moon.[12]

The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. In 1975 the Venera 9 was the first to return images from the surface of another planet. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.

The dream of stepping into the outer reaches of Earth’s atmosphere was driven by the fiction of Peter Francis Geraci[13][14][15] and H. G. Wells,[16] and rocket technology was developed to try to realize this vision. The German V-2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when the Soviet Union launched the first man into space, the United States declared itself to be in a “Space Race” with the Soviets.

Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.

Wernher von Braun was the lead rocket engineer for Nazi Germany’s World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the United States to work on their rocket development (“Operation Paperclip”). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA’s Marshall Space Flight Center which developed the Saturn V moon rocket.

Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuzwhich remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Soviet space program.

Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov’s death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.[17][18]

Although the Sun will probably not be physically explored at all, the study of the Sun has nevertheless been a major focus of space exploration. Being above the atmosphere in particular and Earth’s magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth’s surface. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the Apollo Telescope Mount, have been launched and still others have had solar observation as a secondary objective. Parker Solar Probe, planned for a 2018 launch, will approach the Sun to within 1/8th the orbit of Mercury.

Mercury remains the least explored of the Terrestrial planets. As of May 2013, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).

A third mission to Mercury, scheduled to arrive in 2020, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the Solar System, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the Solar System. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970, Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

Space exploration has been used as a tool to understand Earth as a celestial object in its own right. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen radiation belts was unknown until their discovery by the United States’ first artificial satellite, Explorer 1. These belts contain radiation trapped by Earth’s magnetic fields, which currently renders construction of habitable space stations above 1000km impractical. Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth’s atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon’s surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the Lunokhod program in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Crewed exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the Apollo 11 mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit there, and the next, Exploration Mission 2, is due to orbit the Moon in 2021. Robotic missions are still pursued vigorously.

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul[20] which subsists on a diet of Mars probes. This phenomenon is also informally known as the “Mars Curse”.[21] In contrast to overall high failure rates in the exploration of Mars, India has become the first country to achieve success of its maiden attempt. India’s Mars Orbiter Mission (MOM)[22][23][24] is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of 450 Crore (US$73 million).[25][26] The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the Emirates Mars Mission, it is scheduled for launch in 2020. The uncrewed exploratory probe has been named “Hope Probe” and will be sent to Mars to study its atmosphere in detail.[27]

The Russian space mission Fobos-Grunt, which launched on 9 November 2011 experienced a failure leaving it stranded in low Earth orbit.[28] It was to begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a “trans-shipment point” for spaceships traveling to Mars.[29]

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been “flybys”, in which detailed observations are taken without the probe landing or entering orbit; such as in Pioneer and Voyager programs. The Galileo and Juno spacecraft are the only spacecraft to have entered the planet’s orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is nearly impossible.

Reaching Jupiter from Earth requires a delta-v of 9.2km/s,[30] which is comparable to the 9.7km/s delta-v needed to reach low Earth orbit.[31] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[30]

Jupiter has 69 known moons, many of which have relatively little known information about them.

Saturn has been explored only through uncrewed spacecraft launched by NASA, including one mission (CassiniHuygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 known moons, although the exact number is debatable since Saturn’s rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan, which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth. Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the Huygens probe deployed by the Cassini spacecraft.

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on 24 January 1986. Voyager 2 studied the planet’s unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be completely unique and proved to be profoundly affected by the planet’s unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the Moons of Uranus, including evidence that Miranda had been unusually geologically active.

The exploration of Neptune began with the 25 August 1989 Voyager 2 flyby, the sole visit to the system as of 2014. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2’s visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter’s small Spot. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100km/h.[32] Voyager 2 also examined Neptune’s ring and moon system. It discovered 900 complete rings and additional partial ring “arcs” around Neptune. In addition to examining Neptune’s three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager 2 supported the view that Neptune’s largest moon, Triton, is a captured Kuiper belt object.[33]

The dwarf planet Pluto presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn’s moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.[34]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size (and also the first member of the important subclass, defined by orbit and known as “plutinos”). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the United States government in 2003.[35] New Horizons was launched successfully on 19 January 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery. Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo’s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA’s Dawn spacecraft, launched in 2007.

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the International Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition and the Stardust mission returned samples of another comet’s tail. The Philae lander successfully landed on Comet ChuryumovGerasimenko in 2014 as part of the broader Rosetta mission.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space.[36] Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.[37] The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.[38]

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. China has announced plans to have a 60-ton multi-module space station in orbit by 2020.

The NASA Authorization Act of 2010 provided a re-prioritized list of objectives for the American space program, as well as funding for the first priorities. NASA proposes to move forward with the development of the Space Launch System (SLS), which will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment, and science experiments to Earth’s orbit and destinations beyond. Additionally, the SLS will serve as a back up for commercial and international partner transportation services to the International Space Station. The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and reduce development and operations costs. The first developmental flight is targeted for the end of 2017.[39]

The idea of using high level automated systems for space missions has become a desirable goal to space agencies all around the world. Such systems are believed to yield benefits such as lower cost, less human oversight, and ability to explore deeper in space which is usually restricted by long communications with human controllers.[40]

Autonomy is defined by three requirements:[40]

Autonomous technologies would be able to perform beyond predetermined actions. They would analyze all possible states and events happening around them and come up with a safe response. In addition, such technologies can reduce launch cost and ground involvement. Performance would increase as well. Autonomy would be able to quickly respond upon encountering an unforeseen event, especially in deep space exploration where communication back to Earth would take too long.[40]

NASA began its autonomous science experiment (ASE) on Earth Observing 1 (EO-1) which is NASA’s first satellite in the new millennium program Earth-observing series launched on 21 November 2000. The autonomy of ASE is capable of on-board science analysis, replanning, robust execution, and later the addition of model-based diagnostic. Images obtained by the EO-1 are analyzed on-board and downlinked when a change or an interesting event occur. The ASE software has successfully provided over 10,000 science images.[40]

An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars.[41] In order to make such an approach viable, three requirements need to be fulfilled: first, “a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit”; second, “extending flight duration and distance capability to ever-increasing ranges out to Mars”; and finally, “developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin.”[41] Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them in times of greater risk to radiation exposure.[42]

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.[43] It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.[44] As well, it has been argued that space exploration programs help inspire youth to study in science and engineering.[45]

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that “I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”[46]

NASA has produced a series of public service announcement videos supporting the concept of space exploration.[47]

Overall, the public remains largely supportive of both crewed and uncrewed space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is “a good investment”, compared to 21% who did not.[48]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.[49] He argued that humanity’s choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Private spaceflight companies such as SpaceX and Blue Origin, and commercial space stations such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[50] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: , exo, “outside”).[51][52][53] The term “Xenobiology” has been used as well, but this is technically incorrect because its terminology means “biology of the foreigners”.[54] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.[55] In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 17years, 195days. Valeri Polyakov’s record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a “stepping stone” to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.[57]

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of private property, the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of space technology in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of national territorial claims in outer space and on celestial bodies has been specifically proscribed by the Outer Space Treaty, which had been, as of 2012[update], ratified by all spacefaring nations.[58]

The new “Block 5” Falcon 9, which debuted Friday (May 11) with a flawless launch and first-stage landing, will take rocket reusability to bold new heights very soon if everything works out, SpaceX founder and CEO Elon Musk said. Read More

Space exploration is the discovery and exploration of celestial structures in outer space by means of evolving and growing space technology. While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic space probes and human spaceflight.

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.[1]

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States. The launch of the first human-made object to orbit Earth, the Soviet Union’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet Space Program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971. After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS[2] following STS-133 in March 2011, plans for space exploration by the U.S. remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020[3] was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.[4] The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low Earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as EarthMoon L1, the Moon, EarthSun L2, near-Earth asteroids, and Phobos or Mars orbit.[5]

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future crewed space missions. China, Russia, Japan, and India have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 20th and 21st century.

From the 1990s onwards, private interests began promoting space tourism and then public space exploration of the Moon (see Google Lunar X Prize).

The highest known projectiles prior to the rockets of the 1940s were the shells of the Paris Gun, a type of German long-range siege gun, which reached at least 40 kilometers altitude during World War One.[6] Steps towards putting a human-made object into space were taken by German scientists during World War II while testing the V-2 rocket, which became the first human-made object in space on 3 October 1942 with the launching of the A-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V-2 rocket on 10 May 1946.[7] The first images of Earth taken from space followed the same year[8][9] while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V-2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V-2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

The first successful orbital launch was of the Soviet uncrewed Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83kg (183lb), and is believed to have orbited Earth at a height of about 250km (160mi). It had two radio transmitters (20 and 40MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.

The first successful human spaceflight was Vostok 1 (“East 1”), carrying 27-year-old Russian cosmonaut Yuri Gagarin on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin’s flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard’s suborbital flight on Freedom 7. Orbital flight was achieved by the United States when John Glenn’s Friendship 7 orbited Earth on 20 February 1962.

Valentina Tereshkova, the first woman in space, orbited Earth 48 times aboard Vostok 6 on 16 June 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on 15 October 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Divine Vessel 5) spacecraft.

The first artificial object to reach another celestial body was Luna 2 in 1959.[10] The first automatic landing on another celestial body was performed by Luna 9[11] in 1966. Luna 10 became the first artificial satellite of the Moon.[12]

The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. In 1975 the Venera 9 was the first to return images from the surface of another planet. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.

The dream of stepping into the outer reaches of Earth’s atmosphere was driven by the fiction of Peter Francis Geraci[13][14][15] and H. G. Wells,[16] and rocket technology was developed to try to realize this vision. The German V-2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when the Soviet Union launched the first man into space, the United States declared itself to be in a “Space Race” with the Soviets.

Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.

Wernher von Braun was the lead rocket engineer for Nazi Germany’s World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the United States to work on their rocket development (“Operation Paperclip”). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA’s Marshall Space Flight Center which developed the Saturn V moon rocket.

Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuzwhich remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Soviet space program.

Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov’s death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.[17][18]

Although the Sun will probably not be physically explored at all, the study of the Sun has nevertheless been a major focus of space exploration. Being above the atmosphere in particular and Earth’s magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth’s surface. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the Apollo Telescope Mount, have been launched and still others have had solar observation as a secondary objective. Parker Solar Probe, planned for a 2018 launch, will approach the Sun to within 1/8th the orbit of Mercury.

Mercury remains the least explored of the Terrestrial planets. As of May 2013, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).

A third mission to Mercury, scheduled to arrive in 2020, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the Solar System, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the Solar System. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970, Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

Space exploration has been used as a tool to understand Earth as a celestial object in its own right. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen radiation belts was unknown until their discovery by the United States’ first artificial satellite, Explorer 1. These belts contain radiation trapped by Earth’s magnetic fields, which currently renders construction of habitable space stations above 1000km impractical. Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth’s atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon’s surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the Lunokhod program in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Crewed exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the Apollo 11 mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit there, and the next, Exploration Mission 2, is due to orbit the Moon in 2021. Robotic missions are still pursued vigorously.

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul[20] which subsists on a diet of Mars probes. This phenomenon is also informally known as the “Mars Curse”.[21] In contrast to overall high failure rates in the exploration of Mars, India has become the first country to achieve success of its maiden attempt. India’s Mars Orbiter Mission (MOM)[22][23][24] is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of 450 Crore (US$73 million).[25][26] The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the Emirates Mars Mission, it is scheduled for launch in 2020. The uncrewed exploratory probe has been named “Hope Probe” and will be sent to Mars to study its atmosphere in detail.[27]

The Russian space mission Fobos-Grunt, which launched on 9 November 2011 experienced a failure leaving it stranded in low Earth orbit.[28] It was to begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a “trans-shipment point” for spaceships traveling to Mars.[29]

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been “flybys”, in which detailed observations are taken without the probe landing or entering orbit; such as in Pioneer and Voyager programs. The Galileo and Juno spacecraft are the only spacecraft to have entered the planet’s orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is nearly impossible.

Reaching Jupiter from Earth requires a delta-v of 9.2km/s,[30] which is comparable to the 9.7km/s delta-v needed to reach low Earth orbit.[31] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[30]

Jupiter has 69 known moons, many of which have relatively little known information about them.

Saturn has been explored only through uncrewed spacecraft launched by NASA, including one mission (CassiniHuygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 known moons, although the exact number is debatable since Saturn’s rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan, which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth. Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the Huygens probe deployed by the Cassini spacecraft.

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on 24 January 1986. Voyager 2 studied the planet’s unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be completely unique and proved to be profoundly affected by the planet’s unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the Moons of Uranus, including evidence that Miranda had been unusually geologically active.

The exploration of Neptune began with the 25 August 1989 Voyager 2 flyby, the sole visit to the system as of 2014. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2’s visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter’s small Spot. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100km/h.[32] Voyager 2 also examined Neptune’s ring and moon system. It discovered 900 complete rings and additional partial ring “arcs” around Neptune. In addition to examining Neptune’s three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager 2 supported the view that Neptune’s largest moon, Triton, is a captured Kuiper belt object.[33]

The dwarf planet Pluto presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn’s moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.[34]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size (and also the first member of the important subclass, defined by orbit and known as “plutinos”). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the United States government in 2003.[35] New Horizons was launched successfully on 19 January 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery. Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo’s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA’s Dawn spacecraft, launched in 2007.

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the International Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition and the Stardust mission returned samples of another comet’s tail. The Philae lander successfully landed on Comet ChuryumovGerasimenko in 2014 as part of the broader Rosetta mission.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space.[36] Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.[37] The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.[38]

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. China has announced plans to have a 60-ton multi-module space station in orbit by 2020.

The NASA Authorization Act of 2010 provided a re-prioritized list of objectives for the American space program, as well as funding for the first priorities. NASA proposes to move forward with the development of the Space Launch System (SLS), which will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment, and science experiments to Earth’s orbit and destinations beyond. Additionally, the SLS will serve as a back up for commercial and international partner transportation services to the International Space Station. The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and reduce development and operations costs. The first developmental flight is targeted for the end of 2017.[39]

The idea of using high level automated systems for space missions has become a desirable goal to space agencies all around the world. Such systems are believed to yield benefits such as lower cost, less human oversight, and ability to explore deeper in space which is usually restricted by long communications with human controllers.[40]

Autonomy is defined by three requirements:[40]

Autonomous technologies would be able to perform beyond predetermined actions. They would analyze all possible states and events happening around them and come up with a safe response. In addition, such technologies can reduce launch cost and ground involvement. Performance would increase as well. Autonomy would be able to quickly respond upon encountering an unforeseen event, especially in deep space exploration where communication back to Earth would take too long.[40]

NASA began its autonomous science experiment (ASE) on Earth Observing 1 (EO-1) which is NASA’s first satellite in the new millennium program Earth-observing series launched on 21 November 2000. The autonomy of ASE is capable of on-board science analysis, replanning, robust execution, and later the addition of model-based diagnostic. Images obtained by the EO-1 are analyzed on-board and downlinked when a change or an interesting event occur. The ASE software has successfully provided over 10,000 science images.[40]

An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars.[41] In order to make such an approach viable, three requirements need to be fulfilled: first, “a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit”; second, “extending flight duration and distance capability to ever-increasing ranges out to Mars”; and finally, “developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin.”[41] Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them in times of greater risk to radiation exposure.[42]

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.[43] It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.[44] As well, it has been argued that space exploration programs help inspire youth to study in science and engineering.[45]

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that “I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”[46]

NASA has produced a series of public service announcement videos supporting the concept of space exploration.[47]

Overall, the public remains largely supportive of both crewed and uncrewed space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is “a good investment”, compared to 21% who did not.[48]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.[49] He argued that humanity’s choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Private spaceflight companies such as SpaceX and Blue Origin, and commercial space stations such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[50] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: , exo, “outside”).[51][52][53] The term “Xenobiology” has been used as well, but this is technically incorrect because its terminology means “biology of the foreigners”.[54] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.[55] In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 17years, 191days. Valeri Polyakov’s record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a “stepping stone” to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.[57]

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of private property, the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of space technology in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of national territorial claims in outer space and on celestial bodies has been specifically proscribed by the Outer Space Treaty, which had been, as of 2012[update], ratified by all spacefaring nations.[58]

SpaceX debuted the new version of its Falcon 9 rocket, known as the Block 5, on May 11, 2018, with a flawless satellite launch and first-stage landing on a ship at sea. See pictures of the booster and the spaceflight action here. Read More

Space exploration is the discovery and exploration of celestial structures in outer space by means of evolving and growing space technology. While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic space probes and human spaceflight.

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.[1]

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States. The launch of the first human-made object to orbit Earth, the Soviet Union’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet Space Program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971. After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS[2] following STS-133 in March 2011, plans for space exploration by the U.S. remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020[3] was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.[4] The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low Earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as EarthMoon L1, the Moon, EarthSun L2, near-Earth asteroids, and Phobos or Mars orbit.[5]

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future crewed space missions. China, Russia, Japan, and India have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 20th and 21st century.

From the 1990s onwards, private interests began promoting space tourism and then public space exploration of the Moon (see Google Lunar X Prize).

The highest known projectiles prior to the rockets of the 1940s were the shells of the Paris Gun, a type of German long-range siege gun, which reached at least 40 kilometers altitude during World War One.[6] Steps towards putting a human-made object into space were taken by German scientists during World War II while testing the V-2 rocket, which became the first human-made object in space on 3 October 1942 with the launching of the A-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V-2 rocket on 10 May 1946.[7] The first images of Earth taken from space followed the same year[8][9] while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V-2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V-2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

The first successful orbital launch was of the Soviet uncrewed Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83kg (183lb), and is believed to have orbited Earth at a height of about 250km (160mi). It had two radio transmitters (20 and 40MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.

The first successful human spaceflight was Vostok 1 (“East 1”), carrying 27-year-old Russian cosmonaut Yuri Gagarin on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin’s flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard’s suborbital flight on Freedom 7. Orbital flight was achieved by the United States when John Glenn’s Friendship 7 orbited Earth on 20 February 1962.

Valentina Tereshkova, the first woman in space, orbited Earth 48 times aboard Vostok 6 on 16 June 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on 15 October 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Divine Vessel 5) spacecraft.

The first artificial object to reach another celestial body was Luna 2 in 1959.[10] The first automatic landing on another celestial body was performed by Luna 9[11] in 1966. Luna 10 became the first artificial satellite of the Moon.[12]

The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. In 1975 the Venera 9 was the first to return images from the surface of another planet. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.

The dream of stepping into the outer reaches of Earth’s atmosphere was driven by the fiction of Peter Francis Geraci[13][14][15] and H. G. Wells,[16] and rocket technology was developed to try to realize this vision. The German V-2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when the Soviet Union launched the first man into space, the United States declared itself to be in a “Space Race” with the Soviets.

Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.

Wernher von Braun was the lead rocket engineer for Nazi Germany’s World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the United States to work on their rocket development (“Operation Paperclip”). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA’s Marshall Space Flight Center which developed the Saturn V moon rocket.

Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuzwhich remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Soviet space program.

Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov’s death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.[17][18]

Although the Sun will probably not be physically explored at all, the study of the Sun has nevertheless been a major focus of space exploration. Being above the atmosphere in particular and Earth’s magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth’s surface. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the Apollo Telescope Mount, have been launched and still others have had solar observation as a secondary objective. Parker Solar Probe, planned for a 2018 launch, will approach the Sun to within 1/8th the orbit of Mercury.

Mercury remains the least explored of the Terrestrial planets. As of May 2013, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).

A third mission to Mercury, scheduled to arrive in 2020, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the Solar System, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the Solar System. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970, Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

Space exploration has been used as a tool to understand Earth as a celestial object in its own right. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen radiation belts was unknown until their discovery by the United States’ first artificial satellite, Explorer 1. These belts contain radiation trapped by Earth’s magnetic fields, which currently renders construction of habitable space stations above 1000km impractical. Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth’s atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon’s surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the Lunokhod program in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Crewed exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the Apollo 11 mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit there, and the next, Exploration Mission 2, is due to orbit the Moon in 2021. Robotic missions are still pursued vigorously.

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul[20] which subsists on a diet of Mars probes. This phenomenon is also informally known as the “Mars Curse”.[21] In contrast to overall high failure rates in the exploration of Mars, India has become the first country to achieve success of its maiden attempt. India’s Mars Orbiter Mission (MOM)[22][23][24] is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of 450 Crore (US$73 million).[25][26] The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the Emirates Mars Mission, it is scheduled for launch in 2020. The uncrewed exploratory probe has been named “Hope Probe” and will be sent to Mars to study its atmosphere in detail.[27]

The Russian space mission Fobos-Grunt, which launched on 9 November 2011 experienced a failure leaving it stranded in low Earth orbit.[28] It was to begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a “trans-shipment point” for spaceships traveling to Mars.[29]

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been “flybys”, in which detailed observations are taken without the probe landing or entering orbit; such as in Pioneer and Voyager programs. The Galileo and Juno spacecraft are the only spacecraft to have entered the planet’s orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is nearly impossible.

Reaching Jupiter from Earth requires a delta-v of 9.2km/s,[30] which is comparable to the 9.7km/s delta-v needed to reach low Earth orbit.[31] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[30]

Jupiter has 69 known moons, many of which have relatively little known information about them.

Saturn has been explored only through uncrewed spacecraft launched by NASA, including one mission (CassiniHuygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 known moons, although the exact number is debatable since Saturn’s rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan, which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth. Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the Huygens probe deployed by the Cassini spacecraft.

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on 24 January 1986. Voyager 2 studied the planet’s unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be completely unique and proved to be profoundly affected by the planet’s unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the Moons of Uranus, including evidence that Miranda had been unusually geologically active.

The exploration of Neptune began with the 25 August 1989 Voyager 2 flyby, the sole visit to the system as of 2014. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2’s visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter’s small Spot. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100km/h.[32] Voyager 2 also examined Neptune’s ring and moon system. It discovered 900 complete rings and additional partial ring “arcs” around Neptune. In addition to examining Neptune’s three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager 2 supported the view that Neptune’s largest moon, Triton, is a captured Kuiper belt object.[33]

The dwarf planet Pluto presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn’s moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.[34]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size (and also the first member of the important subclass, defined by orbit and known as “plutinos”). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the United States government in 2003.[35] New Horizons was launched successfully on 19 January 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery. Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo’s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA’s Dawn spacecraft, launched in 2007.

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the International Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition and the Stardust mission returned samples of another comet’s tail. The Philae lander successfully landed on Comet ChuryumovGerasimenko in 2014 as part of the broader Rosetta mission.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space.[36] Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.[37] The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.[38]

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. China has announced plans to have a 60-ton multi-module space station in orbit by 2020.

The NASA Authorization Act of 2010 provided a re-prioritized list of objectives for the American space program, as well as funding for the first priorities. NASA proposes to move forward with the development of the Space Launch System (SLS), which will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment, and science experiments to Earth’s orbit and destinations beyond. Additionally, the SLS will serve as a back up for commercial and international partner transportation services to the International Space Station. The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and reduce development and operations costs. The first developmental flight is targeted for the end of 2017.[39]

The idea of using high level automated systems for space missions has become a desirable goal to space agencies all around the world. Such systems are believed to yield benefits such as lower cost, less human oversight, and ability to explore deeper in space which is usually restricted by long communications with human controllers.[40]

Autonomy is defined by three requirements:[40]

Autonomous technologies would be able to perform beyond predetermined actions. They would analyze all possible states and events happening around them and come up with a safe response. In addition, such technologies can reduce launch cost and ground involvement. Performance would increase as well. Autonomy would be able to quickly respond upon encountering an unforeseen event, especially in deep space exploration where communication back to Earth would take too long.[40]

NASA began its autonomous science experiment (ASE) on Earth Observing 1 (EO-1) which is NASA’s first satellite in the new millennium program Earth-observing series launched on 21 November 2000. The autonomy of ASE is capable of on-board science analysis, replanning, robust execution, and later the addition of model-based diagnostic. Images obtained by the EO-1 are analyzed on-board and downlinked when a change or an interesting event occur. The ASE software has successfully provided over 10,000 science images.[40]

An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars.[41] In order to make such an approach viable, three requirements need to be fulfilled: first, “a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit”; second, “extending flight duration and distance capability to ever-increasing ranges out to Mars”; and finally, “developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin.”[41] Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them in times of greater risk to radiation exposure.[42]

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.[43] It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.[44] As well, it has been argued that space exploration programs help inspire youth to study in science and engineering.[45]

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that “I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”[46]

NASA has produced a series of public service announcement videos supporting the concept of space exploration.[47]

Overall, the public remains largely supportive of both crewed and uncrewed space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is “a good investment”, compared to 21% who did not.[48]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.[49] He argued that humanity’s choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Private spaceflight companies such as SpaceX and Blue Origin, and commercial space stations such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[50] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: , exo, “outside”).[51][52][53] The term “Xenobiology” has been used as well, but this is technically incorrect because its terminology means “biology of the foreigners”.[54] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.[55] In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 17years, 190days. Valeri Polyakov’s record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a “stepping stone” to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.[57]

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of private property, the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of space technology in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of national territorial claims in outer space and on celestial bodies has been specifically proscribed by the Outer Space Treaty, which had been, as of 2012[update], ratified by all spacefaring nations.[58]

NASA’s newly appointed administrator, Jim Bridenstine, will make a major speech at the Humans to Mars Summit in Washington, D.C., which takes place today (May 8) through Thursday (May 10). Watch the entire webcast live here at Space.com. Read More

These lists, updated hourly, contain bestselling items. Here you can discover the best Space Exploration Science Fiction eBooks in Amazon Best Sellers, and find the top 100 most popular Amazon Space Exploration Science Fiction eBooks. For non-U.S. customers, Kindle content availability and pricing will vary.

Apollo, Moon-landing project conducted by the U.S. National Aeronautics and Space Administration in the 1960s and 70s. The Apollo program was announced in May 1961, but the choice among competing techniques for achieving a Moon landing and return was not resolved until considerable further study. In the method ultimately employed, a powerful launch vehicle (Saturn V rocket) placed a 50-ton spacecraft in a lunar trajectory. Several Saturn launch vehicles and accompanying spacecraft were built. The Apollo spacecraft were supplied with rocket power of their own, which allowed them to brake on approach to the Moon and go into a lunar orbit. They also were able to release a component of the spacecraft, the Lunar Module (LM), carrying its own rocket power, to land two astronauts on the Moon and bring them back to the lunar orbiting Apollo craft.

The first manned Apollo flight was delayed by a tragic accident, a fire that broke out in the Apollo 1 spacecraft during a ground rehearsal on January 27, 1967, killing all three astronauts. On October 11, 1968, following several unmanned Earth-orbit flights, Apollo 7 made a 163-orbit flight carrying a full crew of three astronauts. Apollo 8 carried out the first step of manned lunar exploration; from Earth orbit it was injected into a lunar trajectory, completed lunar orbit, and returned safely to Earth. Apollo 9 carried out a prolonged mission in Earth orbit to check out the LM. Apollo 10 journeyed to lunar orbit and tested the LM to within 15.2 km (50,000 feet) of the Moons surface. Apollo 11, in July 1969, climaxed the step-by-step procedure with a lunar landing; on July 20 astronaut Neil Armstrong became the first human to set foot on the Moons surface.

Apollo 13, launched in April 1970, suffered an accident caused by an explosion in an oxygen tank but returned safely to Earth. Remaining Apollo missions carried out extensive exploration of the lunar surface, collecting 382 kg (842 pounds) of Moon rocks and installing many instruments for scientific research, such as the solar wind experiment, and the seismographic measurements of the lunar surface. Apollo 17, the final flight of the program, took place in December 1972. In total, 12 American astronauts walked on the Moon during the six successful lunar landing missions of the Apollo program.

A chronology of spaceflights in the Apollo program is shown in the table.

The primary benefit is the survival of the human species, and that’s the only one that really matters; for all others pale in comparison. Possibly within the next 100 years, probably within the next 10,000 years, and definitely within the next 10 million years, the earth wil no longer be able to sustain human civilization, and we’ll have to leave. But more importantly, unless we spread out and populate other planets and moons around ours and other suns, our fate as a species wil be tied to one world, one sun. When the earth dies, we’ll die with it; but even before then it may kill us. Until we colonize space, fill the universe with our progeny, we are bound to the same cycle of extinction that’s claimed 99% of all species that have ever existed. We are a dying species: Maybe we’re already dead. So, to answer your question, the main benefit of space exploitation is human survival. It isn’t about money, pride, knowledge, or power, it’s about our future. Think about that the next time the republicans cut Nasa’s funding.

Apollo, Moon-landing project conducted by the U.S. National Aeronautics and Space Administration in the 1960s and 70s. The Apollo program was announced in May 1961, but the choice among competing techniques for achieving a Moon landing and return was not resolved until considerable further study. In the method ultimately employed, a powerful launch vehicle (Saturn V rocket) placed a 50-ton spacecraft in a lunar trajectory. Several Saturn launch vehicles and accompanying spacecraft were built. The Apollo spacecraft were supplied with rocket power of their own, which allowed them to brake on approach to the Moon and go into a lunar orbit. They also were able to release a component of the spacecraft, the Lunar Module (LM), carrying its own rocket power, to land two astronauts on the Moon and bring them back to the lunar orbiting Apollo craft.

The first manned Apollo flight was delayed by a tragic accident, a fire that broke out in the Apollo 1 spacecraft during a ground rehearsal on January 27, 1967, killing all three astronauts. On October 11, 1968, following several unmanned Earth-orbit flights, Apollo 7 made a 163-orbit flight carrying a full crew of three astronauts. Apollo 8 carried out the first step of manned lunar exploration; from Earth orbit it was injected into a lunar trajectory, completed lunar orbit, and returned safely to Earth. Apollo 9 carried out a prolonged mission in Earth orbit to check out the LM. Apollo 10 journeyed to lunar orbit and tested the LM to within 15.2 km (50,000 feet) of the Moons surface. Apollo 11, in July 1969, climaxed the step-by-step procedure with a lunar landing; on July 20 astronaut Neil Armstrong became the first human to set foot on the Moons surface.

Apollo 13, launched in April 1970, suffered an accident caused by an explosion in an oxygen tank but returned safely to Earth. Remaining Apollo missions carried out extensive exploration of the lunar surface, collecting 382 kg (842 pounds) of Moon rocks and installing many instruments for scientific research, such as the solar wind experiment, and the seismographic measurements of the lunar surface. Apollo 17, the final flight of the program, took place in December 1972. In total, 12 American astronauts walked on the Moon during the six successful lunar landing missions of the Apollo program.

A chronology of spaceflights in the Apollo program is shown in the table.

Space exploration is the ongoing discovery and exploration of celestial structures in outer space by means of continuously evolving and growing space technology. While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic space probes and human spaceflight.

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.[1]

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States. The launch of the first human-made object to orbit Earth, the Soviet Union’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet Space Program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971. After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS[2] following STS-133 in March 2011, plans for space exploration by the US remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020[3] was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.[4] The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low Earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as EarthMoon L1, the Moon, EarthSun L2, near-Earth asteroids, and Phobos or Mars orbit.[5]

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future crewed space missions. China, Russia, Japan, and India have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 20th and 21st century.

From the 1990s onwards, private interests began promoting space tourism and then public space exploration of the Moon (see Google Lunar X Prize).

The highest known projectiles prior to the rockets of the 1940s were the shells of the Paris Gun, a type of German long-range siege gun, which reached at least 40 kilometers altitude during World War One.[6] Steps towards putting a human-made object into space were taken by German scientists during World War II while testing the V-2 rocket, which became the first human-made object in space on 3 October 1942 with the launching of the A-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V-2 rocket on 10 May 1946.[7] The first images of Earth taken from space followed the same year[8][9] while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V-2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V-2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

The first successful orbital launch was of the Soviet uncrewed Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83kg (183lb), and is believed to have orbited Earth at a height of about 250km (160mi). It had two radio transmitters (20 and 40MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.

The first successful human spaceflight was Vostok 1 (“East 1”), carrying 27-year-old Russian cosmonaut Yuri Gagarin on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin’s flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard’s suborbital flight on Freedom 7. Orbital flight was achieved by the United States when John Glenn’s Friendship 7 orbited Earth on 20 February 1962.

Valentina Tereshkova, the first woman in space, orbited Earth 48 times aboard Vostok 6 on 16 June 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on 15 October 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Divine Vessel 5) spacecraft.

The first artificial object to reach another celestial body was Luna 2 in 1959.[10] The first automatic landing on another celestial body was performed by Luna 9[11] in 1966. Luna 10 became the first artificial satellite of the Moon.[12]

The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. In 1975 the Venera 9 was the first to return images from the surface of another planet. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.

The dream of stepping into the outer reaches of Earth’s atmosphere was driven by the fiction of Peter Francis Geraci[13][14][15] and H. G. Wells,[16] and rocket technology was developed to try to realize this vision. The German V-2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when the Soviet Union launched the first man into space, the United States declared itself to be in a “Space Race” with the Soviets.

Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.

Wernher von Braun was the lead rocket engineer for Nazi Germany’s World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the USA to work on U.S. rocket development (“Operation Paperclip”). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA’s Marshall Space Flight Center which developed the Saturn V moon rocket.

Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuzwhich remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Soviet space program.

Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov’s death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.[17][18]

Although the Sun will probably not be physically explored at all, the study of the Sun has nevertheless been a major focus of space exploration. Being above the atmosphere in particular and Earth’s magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth’s surface. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the Apollo Telescope Mount, have been launched and still others have had solar observation as a secondary objective. Parker Solar Probe, planned for a 2018 launch, will approach the Sun to within 1/8th the orbit of Mercury.

Mercury remains the least explored of the Terrestrial planets. As of May 2013, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).

A third mission to Mercury, scheduled to arrive in 2020, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the Solar System, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the Solar System. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970, Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

Space exploration has been used as a tool to understand Earth as a celestial object in its own right. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen radiation belts was unknown until their discovery by the United States’ first artificial satellite, Explorer 1. These belts contain radiation trapped by Earth’s magnetic fields, which currently renders construction of habitable space stations above 1000km impractical. Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth’s atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon’s surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the Lunokhod program in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Crewed exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the Apollo 11 mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit there, and the next, Exploration Mission 2, is due to orbit the Moon in 2021. Robotic missions are still pursued vigorously.

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul[20] which subsists on a diet of Mars probes. This phenomenon is also informally known as the “Mars Curse”.[21] In contrast to overall high failure rates in the exploration of Mars, India has become the first country to achieve success of its maiden attempt. India’s Mars Orbiter Mission (MOM)[22][23][24] is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of 450 Crore (US$73 million).[25][26] The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the Emirates Mars Mission, it is scheduled for launch in 2020. The uncrewed exploratory probe has been named “Hope Probe” and will be sent to Mars to study its atmosphere in detail.[27]

The Russian space mission Fobos-Grunt, which launched on 9 November 2011 experienced a failure leaving it stranded in low Earth orbit.[28] It was to begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a “trans-shipment point” for spaceships traveling to Mars.[29]

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been “flybys”, in which detailed observations are taken without the probe landing or entering orbit; such as in Pioneer and Voyager programs. The Galileo and Juno spacecraft are the only spacecraft to have entered the planet’s orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is nearly impossible.

Reaching Jupiter from Earth requires a delta-v of 9.2km/s,[30] which is comparable to the 9.7km/s delta-v needed to reach low Earth orbit.[31] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[30]

Jupiter has 69 known moons, many of which have relatively little known information about them.

Saturn has been explored only through uncrewed spacecraft launched by NASA, including one mission (CassiniHuygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 known moons, although the exact number is debatable since Saturn’s rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan, which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth. Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the Huygens probe deployed by the Cassini spacecraft.

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on 24 January 1986. Voyager 2 studied the planet’s unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be completely unique and proved to be profoundly affected by the planet’s unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the Moons of Uranus, including evidence that Miranda had been unusually geologically active.

The exploration of Neptune began with the 25 August 1989 Voyager 2 flyby, the sole visit to the system as of 2014. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2’s visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter’s small Spot. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100km/h.[32] Voyager 2 also examined Neptune’s ring and moon system. It discovered 900 complete rings and additional partial ring “arcs” around Neptune. In addition to examining Neptune’s three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager 2 supported the view that Neptune’s largest moon, Triton, is a captured Kuiper belt object.[33]

The dwarf planet Pluto presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn’s moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.[34]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size (and also the first member of the important subclass, defined by orbit and known as “plutinos”). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the United States government in 2003.[35] New Horizons was launched successfully on 19 January 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery. Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo’s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA’s Dawn spacecraft, launched in 2007.

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the International Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition and the Stardust mission returned samples of another comet’s tail. The Philae lander successfully landed on Comet ChuryumovGerasimenko in 2014 as part of the broader Rosetta mission.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space.[36] Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.[37] The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.[38]

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. China has announced plans to have a 60-ton multi-module space station in orbit by 2020.

The NASA Authorization Act of 2010 provided a re-prioritized list of objectives for the American space program, as well as funding for the first priorities. NASA proposes to move forward with the development of the Space Launch System (SLS), which will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment, and science experiments to Earth’s orbit and destinations beyond. Additionally, the SLS will serve as a back up for commercial and international partner transportation services to the International Space Station. The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and reduce development and operations costs. The first developmental flight is targeted for the end of 2017.[39]

The idea of using high level automated systems for space missions has become a desirable goal to space agencies all around the world. Such systems are believed to yield benefits such as lower cost, less human oversight, and ability to explore deeper in space which is usually restricted by long communications with human controllers.[40]

Autonomy is defined by three requirements:[40]

Autonomous technologies would be able to perform beyond predetermined actions. They would analyze all possible states and events happening around them and come up with a safe response. In addition, such technologies can reduce launch cost and ground involvement. Performance would increase as well. Autonomy would be able to quickly respond upon encountering an unforeseen event, especially in deep space exploration where communication back to Earth would take too long.[40]

NASA began its autonomous science experiment (ASE) on Earth Observing 1 (EO-1) which is NASA’s first satellite in the new millennium program Earth-observing series launched on 21 November 2000. The autonomy of ASE is capable of on-board science analysis, replanning, robust execution, and later the addition of model-based diagnostic. Images obtained by the EO-1 are analyzed on-board and downlinked when a change or an interesting event occur. The ASE software has successfully provided over 10,000 science images.[40]

An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars.[41] In order to make such an approach viable, three requirements need to be fulfilled: first, “a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit”; second, “extending flight duration and distance capability to ever-increasing ranges out to Mars”; and finally, “developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin.”[41] Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them in times of greater risk to radiation exposure.[42]

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.[43] It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.[44] As well, it has been argued that space exploration programs help inspire youth to study in science and engineering.[45]

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that “I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”[46]

NASA has produced a series of public service announcement videos supporting the concept of space exploration.[47]

Overall, the public remains largely supportive of both crewed and uncrewed space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is “a good investment”, compared to 21% who did not.[48]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.[49] He argued that humanity’s choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Private spaceflight companies such as SpaceX and Blue Origin, and commercial space stations such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[50] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: , exo, “outside”).[51][52][53] The term “Xenobiology” has been used as well, but this is technically incorrect because its terminology means “biology of the foreigners”.[54] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.[55] In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 17years, 157days. Valeri Polyakov’s record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a “stepping stone” to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.[57]

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of private property, the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of space technology in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of national territorial claims in outer space and on celestial bodies has been specifically proscribed by the Outer Space Treaty, which had been, as of 2012[update], ratified by all spacefaring nations.[58]

Soon after departing the small resort town of Truth or Consequences, New Mexico, the video monitors on the bus come to life. Stars glitter in the night sky, a mystical flute soundtrack lilts, and a narrators voice intones: All that you see around you was at the bottom of the sea. The Conquistadors named the flat desert basin that formed after the sea receded Jornada del Muerto, or Journey of the Dead Man. As the bus lumbers through it, the narrator chronicles humanitys fixation with the mysteries of the sky.

This is the road to Spaceport America, which bills itself as the worlds first purpose-built commercial spaceport. But to believe the tourist-bus video, its not just a dormant industrial park erected with the promise of economic revitalization. Its the latest stop in humankinds ageless reach for the stars.

Spaceport America lies about 20 miles southeast of Truth or Consequences, roughly 50 miles north of Las Cruces, and at a perpetually indeterminate moment in the near future. Although the spaceport has been flight-worthy since 2010, the first launch by its anchor tenant, Virgin Galactic, still hasnt taken off. While the private space industry appears to be at a major turning point elsewhere in the world, its impacts havent quite reached the small New Mexico cities banking on its future. There arent many places where a spaceport like this, meant to service an international community, is feasible. Given the states large and controversial investment in the project, its success or failure might have broad impact on private space travel.

A New Mexico spaceport is only the latest entry in a triumphant time line of military and aerospace innovation in this southwestern state. Our video narrator speeds through Spanish colonialism and westward expansion to highlight the Manhattan Projects work in Los Alamos, to the north, and Operation Paperclip, a secret program that recruited German scientists to the United States after World War II. Among them was Wernher von Braun, who brought his V-2 rockets to the state.

White Sands Missile Range, a 3,200-square-mile military-testing site in South Central New Mexicos Tularosa Basin, hosted much of this work. Its home to the Trinity Site, where the first atomic bomb was detonated, and von Brauns rocket testing site, too. Spaceport America is positioned adjacent to the Army property, in a tightly protected airspace. That makes rocket-ship testing a lot easier.

Money is another reason Spaceport America finds itself here. In 2006, thenNew Mexico Governor Bill Richardson struck a partnership with Richard Bransons Virgin Galactic to build the companys headquarters in New Mexico. The state paid for the $220 million in construction costs with public funds, some of which came directly from neighboring Doa Ana and Sierra counties via gross-receipts-tax increases. Those taxes are expected to deliver nearly $75 million by 2029. In exchange, the locals long for economic opportunity. They could use it; according to U.S. Census data, Sierra County has one of the lowest median household incomes of the 33 counties in the state of New Mexico.

Mandy Guss, a business-development administrator with the City of Las Cruces, is optimistic about the spaceports potential impact on the citys future and identity.* It feels exciting, its like the future is now, she says. I think its something thats going to put Las Cruces and our region on the map. In addition to the ripple effects of about 90 projected Virgin Galactic employees relocating to Las Cruces (as of last summer, 21 were already there), the city eagerly anticipates more aerospace companies setting up shop at the spaceport and in Las Cruces.

Steve Green, the mayor of Truth or Consequences, recognizes that a town of less than 6,500 primarily known for its hot springs (the city changed its name from Hot Springs in 1950, in homage to a popular quiz show; locals call the place T or C) isnt likely to see the same population spike: I am realistic enough to understand that Las Cruces will get the lions share of the people who are coming there. We will get the people who dont want the big-city life. But Green is bullish on the tourism opportunities the spaceport will bring once the commercial spaceflights begin.

If they begin. For now, the spaceport is a futurist tourist attraction, not an operational harbor to the cosmos. The tour buses depart from a former T or C community center twice a day every Saturday. They pass thrift stores, RV parks, and bland but durable-looking structures, defiant underdogs against the mountains. We pass the Elephant Butte Dam, a stunning example of early-20th-century Bureau of Reclamation engineering that made it possible for agriculture to thrive in southern New Mexico; even so, a fellow spaceport tourist notes that the water levels seem far lower than what he recalls from childhood.

Spaceport Americas architecture involves monolithic concrete domes and curved forms in weathered earth tones, unobtrusively impressive, like an architectural humblebrag. The complex and its buildings vaguely recall a Southwest landmark frequently mistaken for the city of the future: Arcosanti, the architect Paolo Soleris 1970 urban laboratory nestled in the mountains north of Phoenix. Its oddly fitting: Soleri imagined a sustainable desert utopia, as well as speculative space arcologiesself-sustaining architectural ecologies, delicately rendered as hypothetical asteroid-belt cities or prototype ships.

At times, the spaceport feels as much like a prototype as Soleris drawings. The official tours are daytime weekend affairs, so when we enter the Operations Center on the weekly Saturday tour it feels empty. We are told that work happens at the spaceport, but theres little sign of it. At the Virgin Galactic office building, masking tape marks the carpet floors, perhaps in anticipation of future furniture arrangements. The only spacecraft we see on the tour is a model of Virgin Galactics SpaceShipTwo, glimpsed from a distance in an otherwise empty hangar. Even the spacecraft isnt real.

Admittedly, the name Spaceport America suggests theatrics. There are several commercial spaceports throughout the United States, some of which sport more activity and tenants. Most of Virgin Galactics testing has happened at the Mojave Air and Space Port; Virginias Mid-Atlantic Regional Spaceport recently signed on the SpaceX competitor Vector as a customer.

Others, like Oklahomas Air and Space Port, seem to be even more like ghost towns than this one. But New Mexicos gambit suggests we are at the spaceport of the nation. It doesnt feel like the frontier of private space travel so much as a movie set.

Its a quintessential American desert trope: the future as rehearsal rather than reality. Many promises for technologies of future urbanism start as desert prototypes. Hyperloop Ones test track in the Nevada desert; self-driving cars tooling around Tempe, Arizona; and Bill Gatess Belmont, Arizona, smart-city pilot offer a few more recent examples, but that tendency to treat the desert as blank canvas for constructing utopia resonates from the Mormon state of Deseret to Burning Mans Black Rock City. New Mexico examples tend to include slightly more dystopian rehearsals: Much of the states existing science and defense industries emerged from bringing Manhattan Project scientists to what, at the time, was the middle of nowhere to test nuclear weaponsessentially, to practice ending the world.

Spaceport America hasnt done much rehearsing, yet (although it has, in fact, been literally used as a movie setmost recently for the 2017 sad-teen-from-Mars feature The Space Between Us). Following a disastrous 2014 test flight in the Mojave desert that left the pilot seriously injured and the copilot dead, Virgin Galactic postponed its plans while addressing what the National Transportation Safety Board called a failure to consider and protect against the possibility that a single human error could result in a catastrophic hazard. A successful flight in January 2018 has restored some confidence that, at long last, space tourism really is around the corner. Down in Las Cruces, Guss expressed cautious optimism. Youll always have a lot of folks who, you know, wont believe it till they see it. But overall people are hopeful and excited.

Notwithstanding Virgin Galactics absence, there is a lot already happening at the spaceport. The tourism at the heart of the Spaceport America pitch hasnt yet materialized, but meta-tourism like the Saturday tours provide some revenue, and the aerospace industry has been active here. Google tested its SkyBender project to beam high-speed internet via drone there. Spaceport America boasts of its 39 vertical launches and seven horizontal launches, which have included launches by UP Aerospace in partnership with White Sands and the launching of various human cremains into space by the memorial spaceflight provider Celestis. On the tour, one of the firefighters on-site points to a hangar rented by Boeing holding the CST-100 Starliner, a space capsule the company is testing.

Aerospace successes outside of New Mexico are also encouraging to the spaceports supporters: Shortly after my visit, SpaceXs Falcon Heavy rocket successfully launched Elon Musks Tesla into orbit, along with even greater optimism for the future of the private space industry. (SpaceX was briefly slated to be a regular Spaceport America tenant but has since shifted its ambitions toward a private site in Brownsville, Texas.)

But when its not inviting the public to take in a spectacle, the space industry treats most of its activities as closely guarded trade secretsso much so that the spaceports public financing and ownership has been deemed a major liability. This was the reason that the New Mexico legislature voted overwhelmingly in favor of a bill that gives the spaceport significant exemptions from public-records requests. The Spaceport America CEO, Dan Hicks, argued that companies that might have come to New Mexico were choosing competitor sites out of fear that competitors could glean information about their R&D through records requests. The legislature agreed; during the same session, it also allocated $10 million to Spaceport America for a new hangar and additional operations.

Some last-minute revisions to the bill appeased government-transparency advocates, but the exemptions are subject to Spaceport Americas interpretation. Its unclear, for example, whether Spaceport America could exempt tenants from disclosing information about toxic chemical spills or other environmental disasters (an attempted amendment on this issue by the state legislator Jeff Steinborn failed to pass). Spaceport America acknowledges the validity of the concerns but insists that the bill as passed effectively addresses them.

For the cities that view the spaceport as potentially economically transformative, the records-request exemptions are seen as a cost of doing business. I think that New Mexico has to grow up, Green, the T or C mayor, told me when asked about the potential slippery slope of giving exceptions to publicly financed projects. I dont see why the public has to know what SpaceX or Boeing or Virgin Galactic are doing, what technology theyre dealing with. Thats their business. You want to know about it? Buy their stock.

The NMPolitics.net editor Heath Haussamen, who has been reporting on the public-records issue, believes success isnt predicated on secrecy. I hope the spaceport works, he says. Ive lived here all my life. My daughters six years old. And New Mexicos greatest export is our childrenwe do a great job of giving them college degrees and not giving them opportunities in the state. He appreciates the efforts the state has made to think longer term about the spaceports impact; a portion of the taxes paid by Sierra and Doa Ana County, for example, are dedicated to expanding and supporting STEM education in the counties schools. Haussamen believes Spaceport America could help revitalize the southern New Mexico economy, but he also believes that the public has a right and a duty to be able to know what kind of return theyre getting on their investment.

Perhaps the insistence on secrecy for its tenants explains why Spaceport Americas marketing materials, along with conversations on the official tour, still emphasize Virgin Galactics space-tourism business. Passengers who can afford the $250,000 fare spend several minutes in zero gravity before returning to Earth. Its a far cry from democratizing space travel and pretty unlikely to be the primary source of Spaceport Americas revenue. Virgin Galactics notable absence at the spaceport makes these crewed missions seem like stunt more than science, but most of my fellow tourists take the premise of ubiquitous space travel to colonies on Mars as a fait accompli. Im not sure why people in a desert would fantasize about going somewhere even harder to inhabit.

But the mythologies of the former American frontier tend to collide with the final frontier: As extreme environments, deep space and remote desert have a lot in common. That explains projects like Utahs Mars Desert Research Station, a faux-Martian habitat for long-duration fieldwork for a hypothetical, future Martian expedition. Humanity dreams of going to space for many of the same reasons some people went to the desert: because it is there, because they hope to get rich extracting natural resources they find there, and because they suspect mysterious, new terrains cant be any worse than the irredeemable wreckage of the landscape theyre leaving behind. In a region defined by boom-and-bust cycles of mining and oil and gas, where the future has always been in part determined by the art of water-rights negotiations, and where climate change presents a very real threat (more than half of the state of New Mexico is currently experiencing severe drought), believing in the inevitability of Mars colonies is maybe no less idealistic than believing in the Southwest itself.

This is perhaps the most unavoidable and disconcerting truth of Spaceport America. The romance and promise of the American West was built, in part, on federal land grants to private corporations that promised to bring boomtowns to places previously otherwise deemed uninhabitable wastelands. Cities rose and fell with the rerouting of railroads; a major turning point in Las Cruces own history came when the city sold right-of-way to the Atchison, Topeka, and Santa Fe Railway in the 1880s, making the city part of a crucial industrial thoroughfare.

To manifest destinys proponents, to doubt the inevitability of technological and social progress via the railroad was tantamount to doubting the will of God. Today, questioning the value of (mostly) privately funded space development likewise feels like doubting human progress. Spaceport America isnt all that different from the railroad and mining executives building company towns that it cites in its own promotional literaturewhich is to say, it uses the promise of progress as a smoke screen from very real concerns over taxpayer funding and public accountability. The romance of space distracts from the reality that at the end of the day, Spaceport America is a publicly financed resource mainly serving private companies, built on a long-stalled promise of bringing new money and a daring new tech industry to a jobs-hungry and very poor region. The price tag and PR rhetoric may differ from that of cities engaged in bidding wars over a Facebook data center or a new corporate tech campus, but concerns over public concessions to private-industry demands for secrecy and tax breaks (along with questions of whether the projects benefits will actually be felt by residents who need them the most) remain more or less the same.

On the bus ride back to the Truth or Consequences visitors center, yet another video celebrates the possible democratization of space through the can-do efficiency of the private sector. New Mexico, we are reminded, has been part of that journey this whole time, from petroglyphs to spaceships. Perhaps Spaceport America is part of a grand southwestern historybut a fraught history, and one that provides no guarantee of inevitable success. Whether on the empty spaceport runway or driving across New Mexico, Arizona, Utah, Nevada, or California, it is hard to escape the ghosts of the Wests promised cities of tomorrow among its present cities hanging onto borrowed time.

Watching a group of bored cows on the Jornada del Muerto as Spaceport America recedes into the distance, I wonder if the future always feels like rehearsal until it arrives, or if it is always rehearsal, only seeming like it has arrived when the run-through loses its novelty. Maybe all of the impatient skeptics will be proven wrong this year, and the future will finally arrive at Spaceport America. Here in the desert, a better future always seems to be right around the corner.

Information about the United States space flight programs, including NASA missions and the astronauts who participate in the efforts to explore Earths galaxy.

This timeline is mainly compiled from the NASA Space Exploration Timeline: 1957 A.D.-Present, Sea and Skys Space Exploration Timeline and Timeline of NASA, the Space Shuttle and Near Earth Space Flights.

Space exploration is the ongoing discovery and exploration of celestial structures in outer space by means of continuously evolving and growing space technology. While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic space probes and human spaceflight.

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.[1]

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States. The launch of the first human-made object to orbit Earth, the Soviet Union’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet Space Program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971. After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS[2] following STS-133 in March 2011, plans for space exploration by the US remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020[3] was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.[4] The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low Earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as EarthMoon L1, the Moon, EarthSun L2, near-Earth asteroids, and Phobos or Mars orbit.[5]

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future crewed space missions. China, Russia, Japan, and India have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 20th and 21st century.

From the 1990s onwards, private interests began promoting space tourism and then public space exploration of the Moon (see Google Lunar X Prize).

The highest known projectiles prior to the rockets of the 1940s were the shells of the Paris Gun, a type of German long-range siege gun, which reached at least 40 kilometers altitude during World War One.[6] Steps towards putting a human-made object into space were taken by German scientists during World War II while testing the V-2 rocket, which became the first human-made object in space on 3 October 1942 with the launching of the A-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V-2 rocket on 10 May 1946.[7] The first images of Earth taken from space followed the same year[8][9] while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V-2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V-2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

The first successful orbital launch was of the Soviet uncrewed Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83kg (183lb), and is believed to have orbited Earth at a height of about 250km (160mi). It had two radio transmitters (20 and 40MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.

The first successful human spaceflight was Vostok 1 (“East 1”), carrying 27-year-old Russian cosmonaut Yuri Gagarin on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin’s flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard’s suborbital flight on Freedom 7. Orbital flight was achieved by the United States when John Glenn’s Friendship 7 orbited Earth on 20 February 1962.

Valentina Tereshkova, the first woman in space, orbited Earth 48 times aboard Vostok 6 on 16 June 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on 15 October 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Divine Vessel 5) spacecraft.

The first artificial object to reach another celestial body was Luna 2 in 1959.[10] The first automatic landing on another celestial body was performed by Luna 9[11] in 1966. Luna 10 became the first artificial satellite of the Moon.[12]

The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. In 1975 the Venera 9 was the first to return images from the surface of another planet. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.

The dream of stepping into the outer reaches of Earth’s atmosphere was driven by the fiction of Peter Francis Geraci[13][14][15] and H.G.Wells,[16] and rocket technology was developed to try to realize this vision. The German V-2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when the Soviet Union launched the first man into space, the United States declared itself to be in a “Space Race” with the Soviets.

Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.

Wernher von Braun was the lead rocket engineer for Nazi Germany’s World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the USA to work on U.S. rocket development (“Operation Paperclip”). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA’s Marshall Space Flight Center which developed the Saturn V moon rocket.

Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuzwhich remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Soviet space program.

Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov’s death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.[17][18]

Although the Sun will probably not be physically explored at all, the study of the Sun has nevertheless been a major focus of space exploration. Being above the atmosphere in particular and Earth’s magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth’s surface. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the Apollo Telescope Mount, have been launched and still others have had solar observation as a secondary objective. Parker Solar Probe, planned for a 2018 launch, will approach the Sun to within 1/8th the orbit of Mercury.

Mercury remains the least explored of the Terrestrial planets. As of May 2013, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).

A third mission to Mercury, scheduled to arrive in 2020, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the Solar System, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the Solar System. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970, Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

Space exploration has been used as a tool to understand Earth as a celestial object in its own right. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen radiation belts was unknown until their discovery by the United States’ first artificial satellite, Explorer 1. These belts contain radiation trapped by Earth’s magnetic fields, which currently renders construction of habitable space stations above 1000km impractical. Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth’s atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon’s surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the Lunokhod program in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Crewed exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the Apollo 11 mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit there, and the next, Exploration Mission 2, is due to orbit the Moon in 2021. Robotic missions are still pursued vigorously.

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul[20] which subsists on a diet of Mars probes. This phenomenon is also informally known as the “Mars Curse”.[21] In contrast to overall high failure rates in the exploration of Mars, India has become the first country to achieve success of its maiden attempt. India’s Mars Orbiter Mission (MOM)[22][23][24] is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of 450 Crore (US$73 million).[25][26] The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the Emirates Mars Mission, it is scheduled for launch in 2020. The uncrewed exploratory probe has been named “Hope Probe” and will be sent to Mars to study its atmosphere in detail.[27]

The Russian space mission Fobos-Grunt, which launched on 9 November 2011 experienced a failure leaving it stranded in low Earth orbit.[28] It was to begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a “trans-shipment point” for spaceships traveling to Mars.[29]

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been “flybys”, in which detailed observations are taken without the probe landing or entering orbit; such as in Pioneer and Voyager programs. The Galileo and Juno spacecraft are the only spacecraft to have entered the planet’s orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is nearly impossible.

Reaching Jupiter from Earth requires a delta-v of 9.2km/s,[30] which is comparable to the 9.7km/s delta-v needed to reach low Earth orbit.[31] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[30]

Jupiter has 69 known moons, many of which have relatively little known information about them.

Saturn has been explored only through uncrewed spacecraft launched by NASA, including one mission (CassiniHuygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 known moons, although the exact number is debatable since Saturn’s rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan, which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth. Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the Huygens probe deployed by the Cassini spacecraft.

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on 24 January 1986. Voyager 2 studied the planet’s unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be completely unique and proved to be profoundly affected by the planet’s unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the Moons of Uranus, including evidence that Miranda had been unusually geologically active.

The exploration of Neptune began with the 25 August 1989 Voyager 2 flyby, the sole visit to the system as of 2014. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2’s visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter’s small Spot. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100km/h.[32] Voyager 2 also examined Neptune’s ring and moon system. It discovered 900 complete rings and additional partial ring “arcs” around Neptune. In addition to examining Neptune’s three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager 2 supported the view that Neptune’s largest moon, Triton, is a captured Kuiper belt object.[33]

The dwarf planet Pluto presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn’s moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.[34]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size (and also the first member of the important subclass, defined by orbit and known as “plutinos”). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the United States government in 2003.[35] New Horizons was launched successfully on 19 January 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery. Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo’s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA’s Dawn spacecraft, launched in 2007.

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the International Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition and the Stardust mission returned samples of another comet’s tail. The Philae lander successfully landed on Comet ChuryumovGerasimenko in 2014 as part of the broader Rosetta mission.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space.[36] Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.[37] The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.[38]

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. China has announced plans to have a 60-ton multi-module space station in orbit by 2020.

The NASA Authorization Act of 2010 provided a re-prioritized list of objectives for the American space program, as well as funding for the first priorities. NASA proposes to move forward with the development of the Space Launch System (SLS), which will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment, and science experiments to Earth’s orbit and destinations beyond. Additionally, the SLS will serve as a back up for commercial and international partner transportation services to the International Space Station. The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and reduce development and operations costs. The first developmental flight is targeted for the end of 2017.[39]

The idea of using high level automated systems for space missions has become a desirable goal to space agencies all around the world. Such systems are believed to yield benefits such as lower cost, less human oversight, and ability to explore deeper in space which is usually restricted by long communications with human controllers.[40]

Autonomy is defined by three requirements:[40]

Autonomous technologies would be able to perform beyond predetermined actions. They would analyze all possible states and events happening around them and come up with a safe response. In addition, such technologies can reduce launch cost and ground involvement. Performance would increase as well. Autonomy would be able to quickly respond upon encountering an unforeseen event, especially in deep space exploration where communication back to Earth would take too long.[40]

NASA began its autonomous science experiment (ASE) on Earth Observing 1 (EO-1) which is NASA’s first satellite in the new millennium program Earth-observing series launched on 21 November 2000. The autonomy of ASE is capable of on-board science analysis, replanning, robust execution, and later the addition of model-based diagnostic. Images obtained by the EO-1 are analyzed on-board and downlinked when a change or an interesting event occur. The ASE software has successfully provided over 10,000 science images.[40]

An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars.[41] In order to make such an approach viable, three requirements need to be fulfilled: first, “a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit”; second, “extending flight duration and distance capability to ever-increasing ranges out to Mars”; and finally, “developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin.”[41] Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them in times of greater risk to radiation exposure.[42]

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.[43] It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.[44] As well, it has been argued that space exploration programs help inspire youth to study in science and engineering.[45]

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that “I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”[46]

NASA has produced a series of public service announcement videos supporting the concept of space exploration.[47]

Overall, the public remains largely supportive of both crewed and uncrewed space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is “a good investment”, compared to 21% who did not.[48]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.[49] He argued that humanity’s choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Private spaceflight companies such as SpaceX and Blue Origin, and commercial space stations such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[50] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: , exo, “outside”).[51][52][53] The term “Xenobiology” has been used as well, but this is technically incorrect because its terminology means “biology of the foreigners”.[54] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.[55] In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 17years, 143days. Valeri Polyakov’s record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a “stepping stone” to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.[57]

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of private property, the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of space technology in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of national territorial claims in outer space and on celestial bodies has been specifically proscribed by the Outer Space Treaty, which had been, as of 2012[update], ratified by all spacefaring nations.[58]

Apollo, Moon-landing project conducted by the U.S. National Aeronautics and Space Administration in the 1960s and 70s. The Apollo program was announced in May 1961, but the choice among competing techniques for achieving a Moon landing and return was not resolved until considerable further study. In the method ultimately employed, a powerful launch vehicle (Saturn V rocket) placed a 50-ton spacecraft in a lunar trajectory. Several Saturn launch vehicles and accompanying spacecraft were built. The Apollo spacecraft were supplied with rocket power of their own, which allowed them to brake on approach to the Moon and go into a lunar orbit. They also were able to release a component of the spacecraft, the Lunar Module (LM), carrying its own rocket power, to land two astronauts on the Moon and bring them back to the lunar orbiting Apollo craft.

The first manned Apollo flight was delayed by a tragic accident, a fire that broke out in the Apollo 1 spacecraft during a ground rehearsal on January 27, 1967, killing all three astronauts. On October 11, 1968, following several unmanned Earth-orbit flights, Apollo 7 made a 163-orbit flight carrying a full crew of three astronauts. Apollo 8 carried out the first step of manned lunar exploration; from Earth orbit it was injected into a lunar trajectory, completed lunar orbit, and returned safely to Earth. Apollo 9 carried out a prolonged mission in Earth orbit to check out the LM. Apollo 10 journeyed to lunar orbit and tested the LM to within 15.2 km (50,000 feet) of the Moons surface. Apollo 11, in July 1969, climaxed the step-by-step procedure with a lunar landing; on July 20 astronaut Neil Armstrong became the first human to set foot on the Moons surface.

Apollo 13, launched in April 1970, suffered an accident caused by an explosion in an oxygen tank but returned safely to Earth. Remaining Apollo missions carried out extensive exploration of the lunar surface, collecting 382 kg (842 pounds) of Moon rocks and installing many instruments for scientific research, such as the solar wind experiment, and the seismographic measurements of the lunar surface. Apollo 17, the final flight of the program, took place in December 1972. In total, 12 American astronauts walked on the Moon during the six successful lunar landing missions of the Apollo program.

A chronology of spaceflights in the Apollo program is shown in the table.

Apollo, Moon-landing project conducted by the U.S. National Aeronautics and Space Administration in the 1960s and 70s. The Apollo program was announced in May 1961, but the choice among competing techniques for achieving a Moon landing and return was not resolved until considerable further study. In the method ultimately employed, a powerful launch vehicle (Saturn V rocket) placed a 50-ton spacecraft in a lunar trajectory. Several Saturn launch vehicles and accompanying spacecraft were built. The Apollo spacecraft were supplied with rocket power of their own, which allowed them to brake on approach to the Moon and go into a lunar orbit. They also were able to release a component of the spacecraft, the Lunar Module (LM), carrying its own rocket power, to land two astronauts on the Moon and bring them back to the lunar orbiting Apollo craft.

The first manned Apollo flight was delayed by a tragic accident, a fire that broke out in the Apollo 1 spacecraft during a ground rehearsal on January 27, 1967, killing all three astronauts. On October 11, 1968, following several unmanned Earth-orbit flights, Apollo 7 made a 163-orbit flight carrying a full crew of three astronauts. Apollo 8 carried out the first step of manned lunar exploration; from Earth orbit it was injected into a lunar trajectory, completed lunar orbit, and returned safely to Earth. Apollo 9 carried out a prolonged mission in Earth orbit to check out the LM. Apollo 10 journeyed to lunar orbit and tested the LM to within 15.2 km (50,000 feet) of the Moons surface. Apollo 11, in July 1969, climaxed the step-by-step procedure with a lunar landing; on July 20 astronaut Neil Armstrong became the first human to set foot on the Moons surface.

Apollo 13, launched in April 1970, suffered an accident caused by an explosion in an oxygen tank but returned safely to Earth. Remaining Apollo missions carried out extensive exploration of the lunar surface, collecting 382 kg (842 pounds) of Moon rocks and installing many instruments for scientific research, such as the solar wind experiment, and the seismographic measurements of the lunar surface. Apollo 17, the final flight of the program, took place in December 1972. In total, 12 American astronauts walked on the Moon during the six successful lunar landing missions of the Apollo program.

A chronology of spaceflights in the Apollo program is shown in the table.

Space exploration is the ongoing discovery and exploration of celestial structures in outer space by means of continuously evolving and growing space technology. While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic space probes and human spaceflight.

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.[1]

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States. The launch of the first human-made object to orbit Earth, the Soviet Union’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet Space Program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971. After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS[2] following STS-133 in March 2011, plans for space exploration by the US remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020[3] was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.[4] The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low Earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as EarthMoon L1, the Moon, EarthSun L2, near-Earth asteroids, and Phobos or Mars orbit.[5]

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future crewed space missions. China, Russia, Japan, and India have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 20th and 21st century.

From the 1990s onwards, private interests began promoting space tourism and then public space exploration of the Moon (see Google Lunar X Prize).

The highest known projectiles prior to the rockets of the 1940s were the shells of the Paris Gun, a type of German long-range siege gun, which reached at least 40 kilometers altitude during World War One.[6] Steps towards putting a human-made object into space were taken by German scientists during World War II while testing the V-2 rocket, which became the first human-made object in space on 3 October 1942 with the launching of the A-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V-2 rocket on 10 May 1946.[7] The first images of Earth taken from space followed the same year[8][9] while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V-2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V-2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

The first successful orbital launch was of the Soviet uncrewed Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83kg (183lb), and is believed to have orbited Earth at a height of about 250km (160mi). It had two radio transmitters (20 and 40MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.

The first successful human spaceflight was Vostok 1 (“East 1”), carrying 27-year-old Russian cosmonaut Yuri Gagarin on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin’s flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard’s suborbital flight on Freedom 7. Orbital flight was achieved by the United States when John Glenn’s Friendship 7 orbited Earth on 20 February 1962.

Valentina Tereshkova, the first woman in space, orbited Earth 48 times aboard Vostok 6 on 16 June 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on 15 October 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Divine Vessel 5) spacecraft.

The first artificial object to reach another celestial body was Luna 2 in 1959.[10] The first automatic landing on another celestial body was performed by Luna 9[11] in 1966. Luna 10 became the first artificial satellite of the Moon.[12]

The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. In 1975 the Venera 9 was the first to return images from the surface of another planet. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.

The dream of stepping into the outer reaches of Earth’s atmosphere was driven by the fiction of Peter Francis Geraci[13][14][15] and H.G.Wells,[16] and rocket technology was developed to try to realize this vision. The German V-2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when the Soviet Union launched the first man into space, the United States declared itself to be in a “Space Race” with the Soviets.

Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.

Wernher von Braun was the lead rocket engineer for Nazi Germany’s World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the USA to work on U.S. rocket development (“Operation Paperclip”). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA’s Marshall Space Flight Center which developed the Saturn V moon rocket.

Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuzwhich remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Soviet space program.

Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov’s death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.[17][18]

Although the Sun will probably not be physically explored at all, the study of the Sun has nevertheless been a major focus of space exploration. Being above the atmosphere in particular and Earth’s magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth’s surface. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the Apollo Telescope Mount, have been launched and still others have had solar observation as a secondary objective. Parker Solar Probe, planned for a 2018 launch, will approach the Sun to within 1/8th the orbit of Mercury.

Mercury remains the least explored of the Terrestrial planets. As of May 2013, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).

A third mission to Mercury, scheduled to arrive in 2020, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the Solar System, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the Solar System. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970, Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

Space exploration has been used as a tool to understand Earth as a celestial object in its own right. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen radiation belts was unknown until their discovery by the United States’ first artificial satellite, Explorer 1. These belts contain radiation trapped by Earth’s magnetic fields, which currently renders construction of habitable space stations above 1000km impractical. Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth’s atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon’s surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the Lunokhod program in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Crewed exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the Apollo 11 mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit there, and the next, Exploration Mission 2, is due to orbit the Moon in 2021. Robotic missions are still pursued vigorously.

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul[20] which subsists on a diet of Mars probes. This phenomenon is also informally known as the “Mars Curse”.[21] In contrast to overall high failure rates in the exploration of Mars, India has become the first country to achieve success of its maiden attempt. India’s Mars Orbiter Mission (MOM)[22][23][24] is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of 450 Crore (US$73 million).[25][26] The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the Emirates Mars Mission, it is scheduled for launch in 2020. The uncrewed exploratory probe has been named “Hope Probe” and will be sent to Mars to study its atmosphere in detail.[27]

The Russian space mission Fobos-Grunt, which launched on 9 November 2011 experienced a failure leaving it stranded in low Earth orbit.[28] It was to begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a “trans-shipment point” for spaceships traveling to Mars.[29]

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been “flybys”, in which detailed observations are taken without the probe landing or entering orbit; such as in Pioneer and Voyager programs. The Galileo and Juno spacecraft are the only spacecraft to have entered the planet’s orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is nearly impossible.

Reaching Jupiter from Earth requires a delta-v of 9.2km/s,[30] which is comparable to the 9.7km/s delta-v needed to reach low Earth orbit.[31] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[30]

Jupiter has 69 known moons, many of which have relatively little known information about them.

Saturn has been explored only through uncrewed spacecraft launched by NASA, including one mission (CassiniHuygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 known moons, although the exact number is debatable since Saturn’s rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan, which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth. Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the Huygens probe deployed by the Cassini spacecraft.

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on 24 January 1986. Voyager 2 studied the planet’s unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be completely unique and proved to be profoundly affected by the planet’s unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the Moons of Uranus, including evidence that Miranda had been unusually geologically active.

The exploration of Neptune began with the 25 August 1989 Voyager 2 flyby, the sole visit to the system as of 2014. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2’s visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter’s small Spot. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100km/h.[32] Voyager 2 also examined Neptune’s ring and moon system. It discovered 900 complete rings and additional partial ring “arcs” around Neptune. In addition to examining Neptune’s three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager 2 supported the view that Neptune’s largest moon, Triton, is a captured Kuiper belt object.[33]

The dwarf planet Pluto presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn’s moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.[34]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size (and also the first member of the important subclass, defined by orbit and known as “plutinos”). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the United States government in 2003.[35] New Horizons was launched successfully on 19 January 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery. Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo’s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA’s Dawn spacecraft, launched in 2007.

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the International Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition and the Stardust mission returned samples of another comet’s tail. The Philae lander successfully landed on Comet ChuryumovGerasimenko in 2014 as part of the broader Rosetta mission.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space.[36] Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.[37] The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.[38]

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. China has announced plans to have a 60-ton multi-module space station in orbit by 2020.

The NASA Authorization Act of 2010 provided a re-prioritized list of objectives for the American space program, as well as funding for the first priorities. NASA proposes to move forward with the development of the Space Launch System (SLS), which will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment, and science experiments to Earth’s orbit and destinations beyond. Additionally, the SLS will serve as a back up for commercial and international partner transportation services to the International Space Station. The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and reduce development and operations costs. The first developmental flight is targeted for the end of 2017.[39]

The idea of using high level automated systems for space missions has become a desirable goal to space agencies all around the world. Such systems are believed to yield benefits such as lower cost, less human oversight, and ability to explore deeper in space which is usually restricted by long communications with human controllers.[40]

Autonomy is defined by three requirements:[40]

Autonomous technologies would be able to perform beyond predetermined actions. They would analyze all possible states and events happening around them and come up with a safe response. In addition, such technologies can reduce launch cost and ground involvement. Performance would increase as well. Autonomy would be able to quickly respond upon encountering an unforeseen event, especially in deep space exploration where communication back to Earth would take too long.[40]

NASA began its autonomous science experiment (ASE) on Earth Observing 1 (EO-1) which is NASA’s first satellite in the new millennium program Earth-observing series launched on 21 November 2000. The autonomy of ASE is capable of on-board science analysis, replanning, robust execution, and later the addition of model-based diagnostic. Images obtained by the EO-1 are analyzed on-board and downlinked when a change or an interesting event occur. The ASE software has successfully provided over 10,000 science images.[40]

An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars.[41] In order to make such an approach viable, three requirements need to be fulfilled: first, “a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit”; second, “extending flight duration and distance capability to ever-increasing ranges out to Mars”; and finally, “developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin.”[41] Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them in times of greater risk to radiation exposure.[42]

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.[43] It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.[44] As well, it has been argued that space exploration programs help inspire youth to study in science and engineering.[45]

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that “I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”[46]

NASA has produced a series of public service announcement videos supporting the concept of space exploration.[47]

Overall, the public remains largely supportive of both crewed and uncrewed space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is “a good investment”, compared to 21% who did not.[48]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.[49] He argued that humanity’s choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of Earth. Once in space, the motion of a spacecraftboth when unpropelled and when under propulsionis covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Private spaceflight companies such as SpaceX and Blue Origin, and commercial space stations such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[50] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: , exo, “outside”).[51][52][53] The term “Xenobiology” has been used as well, but this is technically incorrect because its terminology means “biology of the foreigners”.[54] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.[55] In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 17years, 134days. Valeri Polyakov’s record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a “stepping stone” to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.[57]

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of private property, the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of space technology in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of national territorial claims in outer space and on celestial bodies has been specifically proscribed by the Outer Space Treaty, which had been, as of 2012[update], ratified by all spacefaring nations.[58]

Although the possibility of exploring space has long excited people in many walks of life, for most of the latter 20th century, only national governments could afford the very high costs of launching people and machines into space. This reality meant that space exploration had to serve very broad interests, and it indeed has done so in a variety of ways. Government space programs have increased knowledge, served as indicators of national prestige and power, enhanced national security and military strength, and provided significant benefits to the general public. In areas where the private sector could profit from activities in space, most notably the use of satellites as telecommunication relays, commercial space activity has flourished without government funding. In the early 21st century, entrepreneurs believed that there were several other areas of commercial potential in space, most notably privately funded space travel.

In the years after World War II, governments assumed a leading role in the support of research that increased fundamental knowledge about nature, a role that earlier had been played by universities, private foundations, and other nongovernmental supporters. This change came for two reasons. First, the need for complex equipment to carry out many scientific experiments and for the large teams of researchers to use that equipment led to costs that only governments could afford. Second, governments were willing to take on this responsibility because of the belief that fundamental research would produce new knowledge essential to the health, the security, and the quality of life of their citizens. Thus, when scientists sought government support for early space experiments, it was forthcoming. Since the start of space efforts in the United States, the Soviet Union, and Europe, national governments have given high priority to the support of science done in and from space. From modest beginnings, space science has expanded under government support to include multibillion-dollar exploratory missions in the solar system. Examples of such efforts include the development of the Curiosity Mars rover, the Cassini-Huygens mission to Saturn and its moons, and the development of major space-based astronomical observatories such as the Hubble Space Telescope.

Soviet leader Nikita Khrushchev in 1957 used the fact that his country had been first to launch a satellite as evidence of the technological power of the Soviet Union and of the superiority of communism. He repeated these claims after Yury Gagarins orbital flight in 1961. Although U.S. Pres. Dwight D. Eisenhower had decided not to compete for prestige with the Soviet Union in a space race, his successor, John F. Kennedy, had a different view. On April 20, 1961, in the aftermath of the Gagarin flight, he asked his advisers to identify a space program which promises dramatic results in which we could win. The response came in a May 8, 1961, memorandum recommending that the United States commit to sending people to the Moon, because dramatic achievements in spacesymbolize the technological power and organizing capacity of a nation and because the ensuing prestige would be part of the battle along the fluid front of the cold war. From 1961 until the collapse of the Soviet Union in 1991, competition between the United States and the Soviet Union was a major influence on the pace and content of their space programs. Other countries also viewed having a successful space program as an important indicator of national strength.

Even before the first satellite was launched, U.S. leaders recognized that the ability to observe military activities around the world from space would be an asset to national security. Following on the success of its photoreconnaissance satellites, which began operation in 1960, the United States built increasingly complex observation and electronic-intercept intelligence satellites. The Soviet Union also quickly developed an array of intelligence satellites, and later a few other countries instituted their own satellite observation programs. Intelligence-gathering satellites have been used to verify arms-control agreements, provide warnings of military threats, and identify targets during military operations, among other uses.

In addition to providing security benefits, satellites offered military forces the potential for improved communications, weather observation, navigation, timing, and position location. This led to significant government funding for military space programs in the United States and the Soviet Union. Although the advantages and disadvantages of stationing force-delivery weapons in space have been debated, as of the early 21st century, such weapons had not been deployed, nor had space-based antisatellite systemsthat is, systems that can attack or interfere with orbiting satellites. The stationing of weapons of mass destruction in orbit or on celestial bodies is prohibited by international law.

Governments realized early on that the ability to observe Earth from space could provide significant benefits to the general public apart from security and military uses. The first application to be pursued was the development of satellites for assisting in weather forecasting. A second application involved remote observation of land and sea surfaces to gather imagery and other data of value in crop forecasting, resource management, environmental monitoring, and other applications. The U.S. and Soviet governments also developed their own satellite-based global positioning systems, originally for military purposes, that could pinpoint a users exact location, help in navigating from one point to another, and provide very precise time signals. These satellites quickly found numerous civilian uses in such areas as personal navigation, surveying and cartography, geology, air-traffic control, and the operation of information-transfer networks. They illustrate a reality that has remained constant for a half centuryas space capabilities are developed, they often can be used for both military and civilian purposes.

Another space application that began under government sponsorship but quickly moved into the private sector is the relay of voice, video, and data via orbiting satellites. Satellite telecommunications has developed into a multibillion-dollar business and is the one clearly successful area of commercial space activity. A related, but economically much smaller, commercial space business is the provision of launches for private and government satellites. In 2004 a privately financed venture sent a piloted spacecraft, SpaceShipOne, to the lower edge of space for three brief suborbital flights. Although it was technically a much less challenging achievement than carrying humans into orbit, its success was seen as an important step toward opening up space to commercial travel and eventually to tourism. Nearly a decade after SpaceShipOne reached space, several firms were poised to carry out such suborbital flights. Suggestions have been made that in the future other areas of space activity, including remote sensing of Earth, utilization of resources found on the Moon and near-Earth asteroids, and the capture of solar energy to provide electric power on Earth, could become successful businesses.

Most space activities have been pursued because they serve some utilitarian purpose, whether increasing knowledge, adding to national power, or making a profit. Nevertheless, there remains a powerful underlying sense that it is important for humans to explore space for its own sake, to see what is there. Although the only voyages that humans have made away from the near vicinity of Earththe Apollo flights to the Moonwere motivated by Cold War competition, there have been recurrent calls for humans to return to the Moon, travel to Mars, and visit other locations in the solar system and beyond. Until humans resume such journeys of exploration, robotic spacecraft will continue to serve in their stead to explore the solar system and probe the mysteries of the universe.